Court of Appeal Supreme Court New South Wales

• Medium Neutral Citation: Wallace v Kam [2012] NSWCA 82
• Hearing dates: 19 September 2011
• Decision date: 13 April 2012
• Before: Allsop P at [1]; Beazley JA at [35]; Basten JA at [156]

Decision

Appeal dismissed with costs.

[Note: The Uniform Civil Procedure Rules 2005 provide (Rule 36.11) that unless the Court otherwise orders, a judgment or order is taken to be entered when it is recorded in the Court's computerised court record system. Setting aside and variation of judgments or orders is dealt with by Rules 36.15, 36.16, 36.17 and 36.18. Parties should in particular note the time limit of fourteen days in Rule 36.16.]

• Catchwords: TORTS - NEGLIGENCE - medical practitioner - duty to warn patient of material risks inherent in proposed surgery - multiple material risks - whether warning was required; TORTS - NEGLIGENCE - medical practitioner - causation - whether failure to warn of material risk that did not eventuate causally connected to injury - Civil Liability Act 2002, s 5D
• Legislation Cited: Civil Liability Act 2002
• Cases Cited: Adeels Palace Pty Ltd v Moubarak; Adeels Palace Pty Ltd v Bou Najem [2009] HCA 48; 239 CLR 420; Bennett v Minister of Community Welfare [1992] HCA 27; 176 CLR 408; Canterbury v Spence 464 F 2d 772, 150 U.S.App.D.C. 263 (1972); Cattanach v Melchior [2003] HCA 38; 215 CLR 1; Chappel v Hart [1998] HCA 55; 195 CLR 232; Chester v Afshar [2004] UKHL 41; [2005] 1 AC 134; Cochran v Wyeth 3 A 3d 673 (Pa Super, 2010); Downer v Veilleux 322 A 2d 82 (Me. 1974); Ellis v Wallsend District Hospital (1989) 17 NSWLR 553; Environment Agency v Empress Car Co (Abertillery) Ltd [1998] UKHL 5; [1999] 2 AC 22; Faulkner v Keffalinos [1970] 45 ALJR 80; Hopp v Lepp [1980] 4 W.W.R. 645, 13 C.C.L.T. 66, 32 N.R. 145, 22 A.R. 361; Hughes v Lord Advocate [1963] UKHL 1; [1963] AC 837; March v Stramare (E & M H) Pty Ltd [1991] HCA 12; 171 CLR 506; Modbury Triangle Shopping Centre v Anzil [2000] HCA 61; 205 CLR 254; Moyes v Lothian Health Board 1990 S.L.T. 444; Pledge v RTA [2004] HCA 13; 205 ALR 56; Reibl v Hughes [1980] 2 S.C.R. 880, 14 C.C.L.T.1, 114 D.L.R. (3d) 1, 33 N.R. 361, J.E. 80-894; Rogers v Whitaker [1992] HCA 58; 175 CLR 479; Rosenberg v Percival [2001] HCA 18; 205 CLR 434; Sidaway v. Governors of Bethlem Royal Hospital [1985] AC 871; Strong v Woolworths Ltd [2012] HCA 5; Tame v NSW [2002] HCA 35; 211 CLR 317; Travel Compensation Fund v Tambree [2005] HCA 69, 224 CLR 627
• Texts Cited: Gerd Gigerenzer in Reckoning with Risk (Penguin, 2002); HLA Hart and Tony Honoré, Causation in the Law, 2nd ed (1985); Michael S Moore, Causation and Responsibility: An Essay in Law, Morals and Metaphysics (OUP, 2010), p 101; Weinrib, "A Step Forward in Factual Causation" (1975) 38 Modern Law Review 518
• Category: Principal judgment
• Parties: Ian Wallace (Appellant); Andrew Kam (Respondent)
• Representation: P Bates; P White (Appellant); D J Higgs SC; M Fordham (Respondent); Gerard Malouf & Partners (Appellant); Tresscox Lawyers (Respondent)
• File Number(s): CA 2007/265252

Decision under appeal

• Citation: Wallace v Ramsay Health Care [2010] NSWSC 518
• Date of Decision: 2010-07-09 00:00:00
• Before: Harrison J
• File Number(s): SC 20412/07

HEADNOTE

[This headnote is not to be read as part of the judgment]

The appellant underwent fusion to alleviate pain caused by an intervertebral disc protrusion in his lumbar spine. After the surgery, the appellant suffered bilateral femoral neurapraxia, or local nerve damage to the thighs. The appellant brought proceedings against the respondent neurosurgeon who performed the surgery, seeking damages in relation to the respondent's failure to warn of the material risks of the operation, namely, the risk of bilateral femoral neurapraxia and a 5 per cent risk of paralysis.

The trial judge held that the respondent breached his duty of care to the appellant by failing to warn of the material risk of bilateral femoral neurapraxia. However, his Honour held that the appellant did not establish that he would have declined the surgery if warned of that risk. Relevantly, his Honour did not make a finding of whether the 5 per cent risk of paralysis was a material risk, which the respondent was under a duty to disclose to the appellant, nor whether he would have declined the operation if warned of that risk. He treated the risk which did not materialise as irrelevant.

The appellant appealed against his Honour's judgment for the respondent.

The issue for determination was whether the trial judge erred (a) in failing to consider a risk that did not eventuate, but might, had an appropriate warning been given, have led the plaintiff not to have the operation and (b) in finding that the only relevant breach of duty was the failure to warn of the risk that in fact materialised, but where a warning would not have led the plaintiff to decline an operation.

Held per Allsop P dismissing the appeal (Basten JA agreeing in part):

(1) The task involved in s 5D(1)(a) is to determine the factual connection between the negligence and the occurrence of the particular harm. It does not incorporate policy or value judgments: [4].

Cited: Strong v Woolworths Ltd

(2) In the circumstances of this case, the enquiry required by s 5D(1)(a) was a full factual analysis of what Dr Kam did and did not say and what Mr Wallace would have done. This was not undertaken: [2], [9].

(3) It is only possible for this Court to resolve the matter by assuming Mr Wallace was not warned of the risk of paralysis and, if so warned, would not have undergone the operation: [11].

(4) In order for a conclusion under s 5D(1)(b) that the scope of liability should not extend, there needs to be a conclusion of the tenuousness of the factual link or some limitation by reference to the rule of responsibility involved. Here, the duty and the rule of responsibility under s 5D(1)(b) are to protect the patient from harm from material inherent risks that are unacceptable to him or her: [12]-[14].

Considered: Rosenberg v Percival; March v Stramare (E & MH) Pty Ltd; Chappel v Hart; Environment Agency v Empress Car Co (Abertillery) Ltd

(5) Where the risks can be seen as separate and distinct, recovery is limited to risks coming home that were material and that should have been disclosed and that were not acceptable to the patient: [18]-[19], [23].

Considered: Rosenberg v Percival

Held per Beazley JA (dissenting):

(1) The question of the materiality of risks is determined objectively in all the circumstances. Whether a risk of a 5 per cent chance of a catastrophic outcome is a material risk is a question of fact for the determination of the trial judge: [67].

Considered: Rogers v Whitaker; Rosenberg v Percival

(2) An undisclosed risk, which is one of a 'cluster of risks', does not need to materialise in order to establish a causative link between the breach of the duty to warn of material risks and the harm suffered: [138].

Distinguished: Rosenberg v Percival

Considered: Hughes v Lord Advocate; Chester v Afshar; Reibl v Hughes; Canterbury v Spence; Downer v Veilleux

Applied: Ellis v Wallsend District Hospital

(3) The trial judge erred in finding that the duty to warn of material risks was confined to the risk of neurapraxia: [151].

(4) The concepts of duty of care and causation are interrelated and any determination of causation must be made with regard to the nature and scope of the relevant duty of care. The statutory principles do not abrogate this relationship: [111], [147]-[148].

Cited: Chappel v Hart; Rosenberg v Percival

(5) The question of whether the warning of the risk of paralysis was in fact given involves questions of fact and it is not appropriate for this court to engage in fact finding on this point: [152]-[153].

Held per Basten JA dismissing the appeal:

(1) Any attempt to treat elements of causation as entirely separate and distinct is doomed to fail in contestable cases, as is a rigid compartmentalisation of duty, breach and causation: [164].

Cited: Rosenberg v Percival

(2) As a matter of principle, if the purpose of requiring payment of compensation is to require the defendant to bear the cost of the harm eventuating from his or her negligent conduct, it is far from clear why that burden should be imposed in circumstances where the harm could only have arisen from breach of another element of the duty: [173].

(3) It is hard to identify a principled basis upon which a medical practitioner should be made legally responsible to pay compensation to a person who suffered an adverse outcome as to which he or she had been properly advised and had accepted: [174].

(4) The failure to warn of the risk which came to pass was not a physical condition necessary for the occurrence of harm, so that aspect of the negligence of the respondent was not a relevant cause of the harm: [175].

Judgment

1 ALLSOP P: I have had the great benefit of reading in draft the reasons of Beazley JA and Basten JA. Though relatively simple in its primary factual matrix, this case reveals the subtleties and difficulties that underlie questions of causation. I have not found the resolution of the case easy. That difficulty stems from the fulcrum around which the question of liability turns: the value judgment involved in deciding whether it is appropriate that Dr Kam should be liable for the harm caused by the manifestation of neurapraxia. I have come to the view that it is not appropriate. I differ somewhat from Basten JA in concluding why the appeal should be dismissed. Given the comprehensive discussion by Beazley JA of the background, facts and authorities, for which I am grateful, I am able to state my reasons shortly.

2 The reasons of the primary judge were, if I may say so, clear, concise and precise. His Honour set out the framework of the causal analysis by reference to the Civil Liability Act 2002 (NSW), s 5D. In my respectful view, however, though his Honour reached the correct conclusion, the analysis by which he reached his conclusion paid insufficient regard to the structure of analysis required by s 5D. In particular, I disagree with his Honour's approach to s 5D(1)(a). The difference in my approach to that adopted by the primary judge broadly conforms to the difference of approach I have to that primarily adopted by Basten JA. In the circumstances of this case, the enquiry required by s 5D(1)(a) required a full factual analysis of what Dr Kam did and did not say and what Mr Wallace would have done. The limitation on the scope of liability of Dr Kam arises from the enquiry and conclusion under s 5D(1)(b).

3 It is thus necessary, first, to say something of the operation of s 5D. The framework within s 5D is the division of the enquiry into "the distinct elements of factual causation and scope of liability ... in line with the recommendations in ... the Ipp Report": Strong v Woolworths Ltd [2012] HCA 5 at [19] (per French CJ, Gummow J, Crennan J and Bell J). See also Adeels Palace Pty Ltd v Moubarak [2009] HCA 48; 239 CLR 420 at 440 [45]. The debt that the authors of the Ipp Report owed to Professor Stapleton that was acknowledged in the Ipp Report reinforces the proposition stated in Strong (above) that the subject of s 5D(1)(a) is a purely factual enquiry and not one in which value judgments are made and into which policy considerations intrude: cf March v Stramare (E & MH) Pty Ltd [1991] HCA 12; 171 CLR 506. That is the burden of much of the scholarship of Professor Stapleton in this area. That conclusion is also, and principally, derived from the words of the statute, by the two words in parentheses: "(factual causation)".

4 Thus, the task involved in s 5D(1)(a) is the elucidation of the factual connection between the negligence (the relevant breach of the relevant duty) and the occurrence of the particular harm. That task should not incorporate policy or value judgments, whether referred to as "proximate cause" or whether dictated by a rule that the factual enquiry should be limited by the relationship between the scope of the risk and what occurred. Such considerations naturally fall within the scope of liability analysis in s 5D(1)(b), if s 5D(1)(a) is satisfied, or in s 5D(2), if it is not.

5 Of course, the factual enquiry in s 5D(1)(a) is governed by the nature and content of the duty and its breach since that is the "negligence" referred to in s 5D(1). It is the connection between that and the harm that is to be analysed, factually.

6 The duty is that described by Mason CJ, Brennan J, Dawson J, Toohey J and McHugh J in Rogers v Whitaker [1992] HCA 58; 175 CLR 479 at 483:

"to exercise reasonable care and skill in the provision of professional advice and treatment ... [being] a 'single comprehensive duty covering all the ways in which a doctor is called upon to exercise his skill and judgment'; it extends to the examination, diagnosis and treatment of the patient and the provision of information in the appropriate case. It is of course necessary to give content to the duty in the given case."

(Citations omitted.)

See also at 489:

"Acceptance of this approach does not entail an artificial division or itemization of specific, individual duties, carved out of the overall duty of care. The duty of a medical practitioner to exercise reasonable care and skill in the provision of advice and treatment is a single comprehensive duty."

7 If a medical procedure has material risks (being risks to which in the circumstances a reasonable person in the patient's position would be likely, if warned, to attach significance or to which the patient would be likely, if warned, to attach significance if the medical practitioner is or should reasonably be aware of that fact) that are inherent, then, leaving to one side the exigencies of emergency or other questions of therapeutic judgment, the scope and content of the duty of care includes a duty to warn the patient of those material inherent risks: Rogers v Whitaker at 487-490, in particular at 490.

8 Whether any set of circumstances where there has been said to be a failure to disclose and appropriately warn of more than one risk may be better viewed as several distinct breaches of the same duty or one interconnected failure to disclose all relevant inherent risks will depend upon a factual enquiry. Here, one operation was being contemplated. The potential benefits and risks of undergoing that operation were all part of the relevant information, as a whole, which the appellant was entitled to have in order to make up his mind, after weighing all relevant information, as to whether to seek the benefits of the procedure, by hazarding such risks as it entailed. It is unrealistic to posit a coherent factual enquiry for the purposes of s 5D(1)(a) by only asking what would have been his decision had he only been told part of what he should have been told. The duty was one comprehensive duty. If it was breached, that occurred, on the appellant's case, by failing to tell him of both possible risks - neurapraxia and paralysis in an appropriately framed and coherent warning that would have enabled him to weigh the benefits and the hazards of the procedure. There are at least two further reasons not to limit the enquiry under s 5D(1)(a) in this way: first, the words of the paragraph and its content do not call for a partial factual enquiry or a factual enquiry truncated by a policy based reason; and secondly, such a truncation may well be factually incoherent. The relationship of the different risks to each other may be close or it may be distant. That may depend upon a number of matters, including the medical relationship of the risks or the attitude or background of the patient.

9 The correct course is to undertake the whole factual enquiry called for by s 5D(1)(a) in order to determine the factual relevance and connection of the negligence to the harm caused.

10 One then turns to the operation of s 5D(1)(b) to assess whether it was "appropriate for the scope of the negligent person's liability to extend to the harm so caused". It is that enquiry which will draw in (without intending to be exhaustive) value judgments, an assessment of the scope of the risks, the type of breaches and risks involved, their relationship to the risk that came home and legal policy questions as to how widely to permit the scope of liability to reach.

11 Strictly speaking, neither enquiry under s 5D(1)(a) or (b) has been undertaken. Factual matters were not found by the primary judge that bear principally upon the enquiry under s 5D(1)(a). For present purposes, those factual matters were what Dr Kam said and what Mr Wallace would have done had full and adequate disclosure been made. These involve assessment of credit and of the witnesses generally. It is not possible for this Court to undertake that factual enquiry. It is only possible for this Court to finalise the matter by assuming that Mr Wallace was not warned of the risk of catastrophic paralysis and if so warned he would not have undergone the operation, and by coming to a view about the operation of s 5D(1)(b) on the facts as they stand.

12 The enquiry and conclusion under s 5D(1)(b) involve a value judgment. In circumstances where s 5D(1)(a) has been satisfied, for the enquiry under (1)(b) to produce an answer that the scope of the liability of the medical practitioner in Dr Kam's position should not extend to the harm that would not have occurred had he or she not been negligent, it is necessary that there be a conclusion either of the tenuousness of the factual link or some limitation by reference to the rule of responsibility involved. For instance, in Chappel v Hart [1998] HCA 55; 195 CLR 232 at 257 [66] and Rosenberg v Percival [2001] HCA 18; 205 CLR 434 at 460 [83], Gummow J gave the example of harm being caused by the misapplication of an anaesthetic in an operation that would not have taken place had the doctor disclosed some inherent medical risk. His Honour characterised the sheeting home of liability as (Chappel at 257 [66]) an "absurd" or "unjust" or (Rosenberg at 460 [83]) an "unacceptable" result that would prevent the law concluding that the negligence caused the harm. This analysis was, of course, at common law under the approach dictated by March v Stramare in which value judgments form part of the process of reasoning about causation. The same kinds of value judgments attend the operation of s 5D(1)(b) (and s 5D(4)), as well as, in another context, s 5D(2). The drawing of a conclusion that a consequence of posited liability would be "unjust", "absurd" or "unacceptable" would be relevant to the conclusion of appropriateness for s 5D(1)(b). Thus, to use the language of the statute, one might restate the point made by Gummow J in his Honour's example by asking whether it is appropriate to extend liability to the defendant where his or her negligence only placed the plaintiff in the place at the time permitting a risk unrelated to that involved in the duty that was breached to come home. If the ceiling of the operating theatre falls in, if the surgeon collapses and strikes the patient, if the anaesthetist misapplies the anaesthetic, if any of countless other things, foreseeable or unforeseeable, go wrong with an operation, a value judgment, based on the rule of responsibility concerned (Environment Agency v Empress Car Co (Abertillery) Ltd [1998] UKHL 5; [1999] 2 AC 22) will have to be made, under s 5D(1)(b). It is in this enquiry that the relationship between the content of the duty (the rule of responsibility), the nature of the risk the subject of the duty and what harm occurred is important: March v Stramare at 516; Faulkner v Keffalinos (1970) 45 ALJR 80 at 86; H L A Hart and T Honoré Causation in the Law (Oxford, 2nd Ed, 1985) at 122.

13 At common law, the ascription of a causal character to a factor without which the harm would not occur, rather than of a non-causal character as a mere condition placing the plaintiff at the place of the harm, depends ultimately on a value judgment (that may well be contestable) made by reference to such (overlapping and at times synonymous) factors as the rule of responsibility and the legal policy underlying it, the content and scope of the duty, the risk addressed by the rule and the duty, the character of the breach, the foreseeability or remoteness of the harm, the intervention of other factors (human and non-human) and their nature, and evaluative common sense. Such considerations also find their place in the enquiry in s 5D(1)(b). Causation is part of the legal analysis concerning whether to attribute legal responsibility and award compensation in a just and coherent way conformable with the legal rule at hand.

14 Here, unlike in the above examples, the harm was factually caused (under s 5D(1)(a)) by the manifestation of an inherent risk that was related to the duty that was breached. The harm here did not occur by the acts or omissions of a third party, or by misapplied anaesthetic, or by some random act or circumstance of the day distinct from the duty to warn. One of the risks, of a number of which Mr Wallace should have been warned, came home. Mr Wallace was in one sense entitled to make his decision on the basis of complete information. That said, the approach to the enquiry under s 5D(1)(b) should reflect the underlying legal aims of the duty and the rule of responsibility: that is, to protect the patient by holding the doctor responsible for the harm that may result from material inherent risks that were not the subject of warning. The duty and the rule of responsibility are not to protect the patient from the risk of an uninformed decision; they are not to protect the integrity of the decision: Rosenberg at 456 [61] and Rogers v Whitaker at 489-490. They are to protect the patient from harm from material inherent risks that are unacceptable to him or her.

15 In the value judgment necessary for s 5D(1)(b), one can readily contemplate circumstances where it was not appropriate to extend the scope of liability, even though a but for test was satisfied. Recovery for the costs of, and inconvenience involved in, an entirely successful operation, in which none of the inherent risks that should have been the subject of a warning came home, might be one. The conclusions that sheeting home such liability would be absurd, unjust, unacceptable or inappropriate would be readily understandable. That conclusion also brings with it the proposition that it is necessary that a risk not warned against come home for there to be an appropriate causal relationship between the breach and the harm. This is the proposition that lies at the heart of the American cases discussed by Beazley JA and referred to below.

16 Another example is that of an inherent risk being clearly disclosed and expressly accepted by the patient, who was content to hazard that risk; that very risk comes home; but the operation would not have been undergone had a quite different risk been disclosed. The factual causal (but for) link may be clear; so, it might be thought, is the injustice or opportunism of the claim. If it is correct to say that injustice and opportunism are suggested by those facts, one is driven to ask what is different about the case here: where the risk that came home was not disclosed, but would, if alone disclosed, have been accepted.

17 In both examples in the previous paragraph, the hazarding of the risk was acceptable to the patient. Unless the further disclosure or disclosures required is or are such that it or they bears or bear on the acceptability of that risk, one would assume that that risk remained acceptable. What was not acceptable was the combination of all the risks such that the procedure became unacceptable. An example of the further disclosure bearing on the acceptability of a risk might be as follows. If the occurrence of neurapraxia was disclosed that risk may have been acceptable in itself with its usual consequences; but if neurapraxia could, in some cases, trigger other catastrophic neurological consequences it would be impossible to say that the risk of neurapraxia had been accepted, even though only the "usual" consequences and discomfortures of it had manifested themselves. But, if neurapraxia was an acceptable risk or hazard, but other risks quite unrelated to it were not, the claim would still be for damage from harm (neurapraxia) the risk of which was acceptable.

18 Of course, these questions are intensely factual involving the relationship between the risks, what risks were acceptable and what were not - whether severally or in combination. Thus, it might not be possible to disentangle one risk from another, in which case the fact that one risk came home would not entitle a conclusion that it should be examined severally. If, however, the risks can be seen as separate and distinct, that is one not bearing on the likelihood of the other occurring, or having no other relevant medical relationship or connection or no known relevant connection for the patient, the policy reasons behind the approach of Gummow J being transferred to the enquiry under s 5D(1)(b) are powerful. By this approach, recovery is limited to risks coming home that were material and that should have been disclosed, and that were not acceptable, in the sense that the patient would not have been willing to hazard that risk for the benefits of the procedure.

19 It is undoubted that the duty is a single comprehensive duty, but the harm for which the doctor should be held liable is the just and appropriate consequences of his or her breach of failing to warn of inherent risks. That, however, should not extend to harm from risks that the patient was willing to hazard, whether through an express choice or as found had their disclosure been made. This limits recovery to what was an unacceptable risk (or risks) and harm therefrom that has (or have) not been the subject of a warning.

20 Here, the relevant findings of the primary judge at [91]-[94] were clear:

"[91] In my opinion the plaintiff would not have declined the surgery if warned of the possibility of this condition in general or specific terms as a risk of the surgery he was contemplating. This is so in my opinion whether the risk is characterised as a risk of bilateral femoral neurapraxia, local nerve damage, weakness in either or both of his legs or in general terms that he could be left temporarily worse off with a condition fitting these descriptions. This is for the following reasons.

[92] As the result of his preoperative condition, as described by him, the plaintiff was desperate for some form of pain relief. He had attended a pain management centre in an effort to try to reduce the pain in his back and legs. He agreed he had had some difficulty attempting to do this. He had tried physiotherapy but this had not helped. He was taking more and more medication with no corresponding benefit. He could only walk with the aid of a walking stick. No conservative measures had worked. Dr New had foreshadowed the need for surgery. The plaintiff was 'absolutely fed up with having to take medication'. He was in a perpetual (medicated) daze. He told Dr New that the fact of the matter was that he was not getting any better. He felt inadequate and useless. He had severe restrictions in movement. This was a cause of significant stress and anxiety. He had bouts of depression because his future was uncertain. He approached Dr Kam for assistance to try to do something about unremitting pain, because he could barely move. Dr Diwan had told him that surgery might be risky. He agreed Dr Kam had told him the same thing. By the time he saw Dr Kam for the second time 'he was desperate for relief'. He could hardly walk. He had tried everything and nothing had worked. He had even had suicidal thoughts. To the suggestion that he was in desperate straits, he agreed he was in a lot of pain. The last resort was to undergo surgery.

[93] A key to understanding what the plaintiff would have done if warned of the risk that in fact materialised is to compare the plaintiff's condition before the operation with the effects of the bilateral femoral neurapraxia itself. There is in my opinion no comparison at all. In a report dated 26 November 2004 addressed to Dr Kam, Dr Awad referred to the bilateral femoral neurapraxia and indicated that the plaintiff's 'power in his legs is slowly improving and he has some anti-gravity movements and he has been slowly mobilised with the physiotherapists'. As earlier recorded, Dr Dowla found that by 25 February 2005 the objective neurophysiological evidence did not support the existence of any definite neuropathic abnormality.

[94] In my opinion, having regard to his desperate preoperative plight, the plaintiff would not have declined the proposed surgery upon the basis of a possible risk of the condition that he suffered in fact. The prospect for this plaintiff of some mild and temporary interference with power and sensation in his lower limbs is out of all proportion to the disabling and distressing condition from which he hoped Dr Kam's surgery would provide a cure or at least some relief. It is to my mind inconceivable, or at the very least highly unlikely, that the plaintiff would have hesitated for a moment to submit to a procedure which he knew to be attended by all of the risks Dr Kam said he informed him of, as well as the risks of which on my finding he should have been informed, in circumstances in which he was in a desperate search for relief from unremitting pain, when there was a 70 to 75 per cent chance of some relief and when the relevant cost to him may have been a mere temporary loss of power and sensation in his lower limbs of the nature, extent and duration of the condition that materialised."

These findings were to the effect that that the risk of neurapraxia was acceptable to Mr Wallace. That risk came home.

21 There was no suggestion that the neurapraxia was medically related to the risk of catastrophic paralysis. On the material, they can be taken to be distinct risks, albeit part of the various matters that should have been disclosed to Mr Wallace in one body of disclosure.

22 I will assume for the purpose of seeking to resolve the appeal that Mr Wallace would not have undergone the operation had he been warned of the 5 per cent risk of catastrophe and that Dr Kam did not disclose this risk. That is to say, however, on the material, that he would not have undergone the operation knowing of the additional and distinct risk of the catastrophic paralysis.

23 The expression of the matter by Gummow J in Rosenberg at 461 [86], though in the context of a single risk, supports the conclusion that extending Dr Kam's liability through the enquiry under s 5D(1)(b) would not be appropriate. To paraphrase what Gummow J said in Rosenberg, it will be appropriate for the scope of liability to extend to circumstances where the doctor fails to warn the patient of a particular consequence and that consequence (reflecting a material risk) in fact eventuates. The rule of responsibility seeks to hold the doctor liable for the consequence of material risks that were not warned of that were unacceptable to the patient.

24 This approach has the support of the United States cases to which Beazley JA refers. The requirement that the undisclosed risk come home in an overwhelming number of jurisdictions (see the citations in Cochran v Wyeth Inc 3 A 3d 673 at 680 (2010)) reflects the widespread acceptance of a qualification of the but for test conformable with notions of legal causation reflected in the use of the phrase "proximate cause". This use of the expression "proximate cause" in this context can be seen to involve the employment of a limiting factor based on legal policy considerations drawn from a value judgment of the kind that falls to be made within s 5D(1)(b), by reference to the content of the duty.

25 It is to be recognised here, however, that the risk that came home, neurapraxia, was undisclosed. If this is where one left the analysis, the words of Circuit Judge Robinson speaking for the Court of Appeals for the District of Columbia in Canterbury v Spence 464 F 2d 772 at 791 [32] (1972) (though necessary to transpose into a situation of multiple risks to be disclosed) might appear to support the appellant's argument, albeit in the context of objective rather than subjective causal analysis:

"If adequate disclosure could reasonably be expected to have caused that person to decline the treatment because of the revelation of the kind of risk or danger that resulted in harm, causation is shown, but otherwise not."

26 One must, however, recognise the importance of the phrase "because of the revelation of the ... risk or danger". The Court in Canterbury v Spence was emphasising the relationship between disclosure and manifestation of the risk. The further relevant fact here is that the primary judge found, with some clarity, that this risk, although undisclosed, was acceptable to Mr Wallace in that it, as a risk distinct from the catastrophic paraplegia, would not have led Mr Wallace to decline the operation. It is the value judgment to be made consequential on that finding that is critical. That value judgment, in the circumstances here where the risks are distinct, in my view, is one that is indistinguishable from that to be made consequent upon disclosure and acceptance of the risk that came home.

27 Further, it is important to understand how the appellant ran his case below. The primary judge described this in [95] of his reasons, as follows:

"Although, as I have found, the plaintiff would have undergone the surgery even if warned of bilateral femoral neurapraxia or local nerve damage, the plaintiff contended that if he was entitled to be, but was not, warned of some risk that would have led him to decline the surgery, he is legally entitled to complain about the consequences of any risk that eventuates, even if that specific risk would not by itself have led him to do so. In this case that translated to a proposition that if the plaintiff would have declined the surgery if warned of some catastrophic outcome of which he was not warned, but which did not materialise, but would not have declined the surgery if warned of bilateral femoral neurapraxia, which did materialise, he is entitled to succeed because the latter condition was caused by the very fact of an operation he would have declined if properly warned."

28 This is also how the matter was in substance put on appeal. This makes clearer the legitimacy of equiparating the value judgments based on actual disclosure and acceptance, on the one hand, and non-disclosure, but a clear finding of acceptability, on the other. Of importance to that equiparation is the separateness and distinctiveness of the risks, which the argument of the appellant below and in this Court implicitly recognised.

29 If I may say so, the passage of Lord Caplan in Moyes v Lothian Health Board 1990 SLT 444 at 447 set out by Beazley JA has a degree of persuasion. Ultimately, however, I am not persuaded that liability for the consequences of multiple inherent risks should not be limited by reference to the considerations suggested by Gummow J and the American cases.

30 In any given case, the facts will need to be examined in a complete enquiry under both (1)(a) and (b) in order that the relationship, if any, between the individual risks be understood. If one risk, being part of a body of risks about all of which there should have been warning, comes home it may be viewed, depending on the precise facts, in particular the medical connection between the risks or the importance of the relationship of the risks to the patient, as not merely the manifestation of that individual risk, but as part of a whole body of inter-related and inter-connected risks that should not be separately examined or analysed. Nor should the examination of the risks disclosed and what risk comes home be examined over-finely. These are medical questions, set in a context of the human and professional activity of warning of risks, the analysis of which is unlikely to be assisted by over refinement.

31 Here, while the primary judge has not undertaken the enquiry expressly under s 5D(1)(b), his approach was in significant respects a substantial enunciation of its elements. I do not see from the material how the risk of neurapraxia and the 5 per cent risk of catastrophic paralysis can be seen other than as distinct matters for disclosure, albeit in the one body of disclosure. The two risks were not said to be related in any particular way. The fundamental argument put by the appellant below and in this Court implicitly recognised this distinction. The finding of the acceptability of the distinct risk that came home was clear and unequivocal in [91]-[94] of the primary judge's reasons. In these circumstances, even making the assumptions that I have, it would not be appropriate to extend to Dr Kam liability for the harm that occurred, and there is no purpose in remitting the matter to the primary judge for further hearing or consideration.

32 Looking at the matter thus, the appeal should be dismissed.

33 Notwithstanding the difficult issues raised, prima facie that dismissal should be followed by an order for costs. If any application is to be made to vary that it should be in the form of a notice of motion supported by submissions and any evidence, filed within 14 days.

34 The orders that I would make are that the appeal be dismissed with costs.

35 BEAZLEY JA: On 22 November 2004, the appellant underwent a six-hour L4/L5 posterior lumbar interbody fusion and pedicle screw fixation (the surgery), performed by the respondent, a neurosurgeon, at Westmead Private Hospital. A further surgical procedure was performed the following morning as a result of the appellant experiencing extreme pain and paralysis in both legs upon regaining consciousness after the surgery. The appellant's difficulties persisted after the further surgical procedure and he was subsequently diagnosed as having suffered bilateral femoral neurapraxia, that is, local nerve damage to the anterior femoral or thigh region of both legs, caused by lying prone for an extended period during the surgery.

36 The appellant commenced proceedings against the respondent claiming damages for breach of duty in failing to warn him of the material risks of the operation. The appellant contended there were two material risks of the operation that the respondent did not disclose to him. The first was the risk of local nerve damage to the thigh, that is, bilateral femoral neurapraxia, as the appellant lay face down on the operating table for an extended period during the surgery. That risk came home. The second risk was a 5 per cent risk of paralysis. That risk arose because the site of the operation was in the spinal cord and there was an inherent risk of injury to the spinal nerves during the course of the operation causing paralysis. This risk was described during argument as a risk of a catastrophic outcome.

37 The trial judge, Harrison J, held that the respondent had breached his duty of care to the appellant in failing to warn of the risk of bilateral femoral neurapraxia. However, as his Honour was not satisfied that the appellant would have declined the surgery had he been warned of that risk, he held that the appellant had failed to establish any causal connection between the respondent's breach of duty and his injury. It followed that the appellant had not proved his cause of action and his claim failed. A verdict was entered for the respondent.

38 The appellant has appealed from the verdict and seeks judgment in his favour in the sum of $350,000, being the amount of damages agreed between the parties at trial in the event the appellant was successful on his claim.

39 The essential issue raised on the appeal was whether the appellant's injury of bilateral femoral neurapraxia was caused by the respondent's breach of duty. On the appellant's argument, the relevant duty was to warn of material risks associated with the surgery and that the respondent breached that duty in failing to warn of the risks of neurapraxia and paralysis. He contended that had he been warned of both risks, and in particular the risk of a catastrophic outcome of paralysis, he would not have undergone the surgery. It followed on this argument that the respondent's breach in failing to warn of the risks of the operation caused the harm that he suffered and he was entitled to succeed on his claim.

Background facts

40 The appellant, who was 57 years of age at the time he underwent the surgery, suffered from a back condition as a result of carrying heavy equipment in the course of his employment. His back condition worsened towards the end of 2003 and this carried over into 2004. He sought medical treatment and underwent a number of investigations and procedures and was diagnosed with an intervertebral disc protrusion in his lumbar spine.

41 The appellant first consulted the respondent in 2004. At that time, he weighed approximately 124 kg and described himself as being "desperate for some relief as [he] could hardly walk". Following the respondent's recommendation that if he lost weight he might obtain some relief, he went on a crash diet and his weight dropped to about 110 kg over approximately three months. However, his back pain did not ease. It also appears that the appellant either regained weight or his estimation of his weight loss was inaccurate as, at the time of surgery, his weight was between 118 kg and 122 kg.

42 At a consultation on 5 October 2004, the respondent recommended immediate surgery. On this occasion the respondent told the appellant that if he did not have surgery, he would end up in a wheelchair, become incontinent and lose control of his bowels. The appellant said that this "really scared the hell out of me" and as he was in so much pain, he agreed to surgery.

43 Following the surgery on 22 November 2004 and the second operation on 23 November 2004, the appellant was hospitalised until 16 February 2005, initially at Westmead Private Hospital and then at St Joseph's Hospital, Auburn. The appellant continued to be significantly disabled after his discharge and at trial his case was that he was an incomplete paraplegic.

The trial judge's reasons

44 The trial judge identified the following issues for determination: (1) whether the respondent breached his duty of care to the appellant by failing to give a proper warning of the risks of the surgery he performed (the breach issue); (2) whether the appellant suffered harm in the circumstances (the injury issue); and (3) if harm was suffered, whether that harm was caused by the respondent's negligence (the causation issue).

45 His Honour found that the appellant sustained bilateral femoral neurapraxia following the surgery on 22 November 2004 and that the further surgical procedure carried out on 23 November 2004 was a consequence of the surgery on 22 November 2004. There is no issue about these findings on the appeal and thus the injury issue can be put to one side.

46 As to breach, the respondent conceded that he had not warned the appellant of the risk of bilateral femoral neurapraxia and that he should have done so. The trial judge found that this risk was an inherent risk of the surgery and was significant in this case because of the appellant's weight. In this regard, the appellant's weight increased both the likelihood of the occurrence of the condition as well as the extent and degree to which it might affect him if it occurred. His Honour held, at [49], that the risk of bilateral femoral neurapraxia was material.

47 Flowing from the respondent's concession as to the need for and his failure to give a warning of bilateral femoral neurapraxia, and his Honour's finding that the risk was material, his Honour held, at [51], that the respondent breached his duty of care to the appellant in failing to warn him of that risk and/or its associated symptoms or consequences. Importantly for the issue on the appeal, his Honour held, at [96], that the failure to warn of bilateral femoral neurapraxia was the only potentially relevant failure to warn.

48 His Honour concluded that if the respondent had warned of this risk, the appellant would nevertheless have undergone the surgery. Hence, the appellant had not satisfied the first limb of the test of causation in the Civil Liability Act 2002, s 5D(1)(a).

49 His Honour made no finding as to whether the respondent had failed to warn the appellant of the 5 per cent risk of paralysis or whether such risk was material. His Honour found that the appellant's allegation that the respondent had failed to warn him of possible catastrophic consequences associated with known risks of the surgery was not relevant, because that risk had not come home. His Honour cited Rosenberg v Percival [2001] HCA 18; 205 CLR 434 in support of this conclusion.

50 Apart from the conceded failure to warn of the risk of bilateral femoral neurapraxia, there was a dispute between the parties regarding what the respondent told the appellant as to the risks of the surgical procedure.

51 The appellant's evidence in chief was that the respondent told him there was a 75 per cent chance of the surgery being successful and did not mention anything that could go wrong, leaving him with the impression that if the surgery was unsuccessful he would simply be the way he was before the surgery. In cross-examination, the appellant said the advice was of a 70-75 per cent chance of the operation being successful. He said he believed there were no negative aspects to the surgery. He reiterated his understanding from what the respondent told him, that the worst that could happen was that he would simply be the way he was before the operation. The appellant also said that the respondent told him that if the operation was successful he would be in no pain at all and would be able to stop taking medication which, prior to surgery, had quadrupled in quantity and strength from when it was first prescribed.

52 The appellant agreed in cross-examination that the respondent specifically told him that any surgery had risks and complications. He also said he understood spinal surgery was "a serious business". He did not recall that the respondent specifically told him there was a risk of injury to his nerve roots and denied that he was told he could be left with weakness in either or both legs. He also denied he was told that he could have spinal cord injury, which could affect either or both of his legs, or that he could develop bladder and bowel incontinence as a result of the surgery. These denials were emphatic. In a later part of the cross-examination, the appellant said he could not remember the bladder and bowel being discussed. All he remembered was that the respondent said if he did not have surgery he would be incontinent. He also denied he was told the surgery could take longer because of his weight.

53 The appellant's wife, who had accompanied the appellant on his consultations with the respondent, also gave evidence. She agreed in cross-examination that the respondent told the appellant that even though he had not lost enough weight, consideration needed to be given to proceeding with the surgery. She agreed the respondent said that any surgery was accompanied by risks and complications and there were no guarantees. She also agreed in cross-examination that the respondent told the appellant there was a risk of nerve root injury. However, she could not remember the respondent saying the appellant could be left with weakness in either or both of his legs after surgery. Nor did she remember if anything was said as to the risk of injury to the spinal cord.

54 The respondent's evidence was that from the time of the first consultation he was concerned with the appellant's weight. His initial recommendation was for the appellant to attempt a significant weight loss program, with surgery as a last resort. The respondent said his advice to the appellant was that if there was no improvement in the appellant's level of pain after the weight loss, he may be a candidate for surgery.

55 The last consultation prior to surgery was on 5 October 2004. At that time, the appellant described his condition as being "really bad. He said that he had not been able to leave the house or get out of bed to go to the kitchen. The respondent observed that the appellant had put on weight. The respondent said that at this time, given the appellant's condition, he again advised that consideration should be given to surgery notwithstanding that the appellant had not lost enough weight.

56 The appellant's wife gave evidence that the respondent told the appellant he had no choice, he had to have surgery and if he did not, he would become incontinent. She said the respondent told the appellant he would be better off with the surgery and that otherwise he would be in a wheelchair, going to the toilet on the chair, and he would have no quality of life.

57 The respondent's evidence was that, having regard to his usual practice when discussing the risks and providing warnings in relation to a proposed fusion and pedicle screw fixation on an obese patient, he would have informed the appellant of the following matters: any surgery was accompanied by potential risks and complications; there were no guarantees with the surgery; there was a risk the appellant could sustain nerve root injury, which could leave him with a weakness in either or both legs; there was a risk of spinal cord injury, which could affect both legs; and there was a risk that he could develop bladder and bowel incontinence after the surgery.

58 The respondent also said he would have advised the appellant that due to his weight and size, the operation would take longer and his recovery would be prolonged. He said that he would have informed the appellant that even if the surgery was uneventful there was a chance that the back pain would not be resolved and would be ongoing. He said he would have informed the appellant that in his case he would estimate the probability of a successful outcome, being a significant decrease in pain, to be about 70 per cent.

59 The respondent stated in his oral evidence that his usual practice was to give a warning that there was roughly a 5 per cent chance of a catastrophic outcome of nerve root injury. No mention had been made of this in his witness statement. The respondent explained this omission as an error. When challenged in cross-examination that he had never informed the appellant of the 5 per cent risk of a catastrophic outcome, the respondent disagreed. He also disagreed that he was telling an untruth in respect of this aspect of his evidence. The respondent agreed in cross-examination that his reference to a 70 per cent likelihood of a successful outcome was not a suggestion that there was a 30 per cent chance of a catastrophic outcome. Rather, he was suggesting there was a 30 per cent chance the appellant's condition would remain the same.

60 The trial judge did not determine the factual dispute between the appellant and the respondent as to whether the respondent informed the appellant of the risk of a 5 per cent catastrophic outcome. He did, however, make observations as to the credit of the appellant, the appellant's wife and the respondent. As to the appellant, his Honour observed that he gave his evidence clearly and apparently truthfully and noted that, in any event, there was no attack upon his credit. His Honour also noted that there was no challenge to the truthfulness of the appellant's wife.

61 However, there had been an attack on the respondent's credit, in that he was challenged as to his version of what he told or at least what, in accordance with his usual practice, he would have told the appellant in relation to the risk of a catastrophic outcome. His Honour commented that the respondent's concession that he had not given a warning about the risk of bilateral femoral neurapraxia or local nerve damage cast the balance of the respondent's evidence in a favourable light. His Honour said, however, that to the extent it was necessary to do so, he found the respondent did not warn the appellant of the risk he could be left with weakness in either or both legs.

Arguments on the appeal

62 The appellant's principal contention on the appeal was that his Honour erred in confining the relevant breach of duty to the failure to warn of the risk of bilateral femoral neurapraxia. The appellant contended that the scope and content of the respondent's duty was to adequately warn the appellant of material risks of the operation, that duty being a "single, comprehensive duty": see Rogers v Whitaker [1992] HCA 58; 175 CLR 479.

63 The appellant submitted that his Honour misapplied Rosenberg v Percival in finding that a failure to warn was not relevantly causative of harm unless the risk in respect of which there was inadequate warning, materialised. His Honour's consequent finding on causation was thereby erroneous. Alternatively, the appellant contended that Rosenberg v Percival ought to have been distinguished by his Honour on the basis that it involved a case where there was only one material risk, not two as was the case here.

64 The appellant contended the respondent had breached his duty of care not only by failing to warn of the risk of bilateral femoral neurapraxia, but also in failing to warn of the 5 per cent risk of a catastrophic outcome. It followed that given the "single, comprehensive" nature of the duty to disclose the material risks inherent in the operation and, on the assumption that there had been a breach of that "single, comprehensive duty", the causation issue had to be determined having regard to the entire breach.

65 The appellant submitted that the correct question for his Honour's determination on the causation issue was whether the appellant would have refused surgery on 22 November 2004 had he been warned, not only of the risk of bilateral femoral neurapraxia, but also of the 5 per cent risk of a catastrophic outcome. The appellant contended that the answer to that question should have been that he would have deferred or refused surgery at that time.

66 The respondent submitted that his Honour correctly determined causation as a matter of principle and as a question of fact. He contended that even if it were to be found that he had not warned of the risk of a catastrophic outcome, it was not appropriate for the scope of his liability to extend to that failure, when that risk had not eventuated.

67 The trial judge did not determine whether the risk of a 5 per cent chance of a catastrophic outcome was material or whether the appellant was warned of that risk. Both involve factual determinations of a different order. The question of materiality is determined objectively in the circumstances of the particular case: see Rogers v Whitaker at 490 (Mason CJ, Brennan, Dawson, Toohey and McHugh JJ); Rosenberg v Percival per Gummow J at 455. A reasonable person, contemplating operative treatment to resolve a condition that was not life threatening and potentially not urgent, may well attach significance to a 5 per cent risk of a catastrophic outcome in making a decision as to whether or not to undergo surgery and the respondent did not suggest to the contrary. It may be that there is no real issue as to the materiality of the risk. However, it is a question of fact for the determination of the trial judge.

68 What the appellant would have done if warned of the risk of paralysis involves a subjective determination in accordance with s 5D(3). Both parties submitted that this Court could determine this question. In doing so, neither party directed attention to the necessity to first determine whether the risk was material. Assuming materiality of the risk, the appellant advanced a number of factual circumstances that he submitted would lead a fact finder to conclude that he would not have had the operation. These matters included: his weight being more than he believed and the respondent not having informed him of his correct weight; the scope for more weight loss before surgery was finally decided upon; the fact that the appellant was under a misapprehension that the back surgery was necessary at that time; that the surgery was not urgent and the respondent's reason for recommending it at that time was the appellant's loss of quality of life, given his failure to lose weight. The appellant also contended that the trial judge overstated the appellant's future mobility restrictions in finding that he would have been housebound and bedridden for many weeks had the surgery not been undertaken at that time.

69 The respondent for his part contended that on the evidence, the Court would find that that the appellant would have had the operation in any event. The respondent referred to the appellant's condition in the weeks immediately preceding the last consultation when he was significantly incapacitated and effectively bedridden due to pain from his condition.

The legal principles

The statute

70 As this case fell to be determined in accordance with the provisions of the Civil Liability Act, the question of causation had to be determined on the basis of the provisions of s 5D. That section provides, relevantly:

"5D General principles

(1) A determination that negligence caused particular harm comprises the following elements:

(a) that the negligence was a necessary condition of the occurrence of the harm (factual causation), and

(b) that it is appropriate for the scope of the negligent person's liability to extend to the harm so caused (scope of liability).

(2) In determining in an exceptional case, in accordance with established principles, whether negligence that cannot be established as a necessary condition of the occurrence of harm should be accepted as establishing factual causation, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party.

(3) If it is relevant to the determination of factual causation to determine what the person who suffered harm would have done if the negligent person had not been negligent:

(a) the matter is to be determined subjectively in the light of all relevant circumstances, subject to paragraph (b), and

(b) any statement made by the person after suffering the harm about what he or she would have done is inadmissible except to the extent (if any) that the statement is against his or her interest.

(4) For the purpose of determining the scope of liability, the court is to consider (amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party."

71 Reference should also be made to s 5E, which provides:

"5E Onus of proof

In determining liability for negligence, the plaintiff always bears the onus of proving, on the balance of probabilities, any fact relevant to the issue of causation."

72 Division 6, s 5O, which makes provision for the standard of care for professionals has no application to cases involving failure to warn: see s 5P, and thus is not relevant to the problem with which the Court is presently concerned.

73 The appellant submitted that in this case s 5D(1)(a), that is, the "but for" test, was satisfied: the respondent's breach of the duty to give him an adequate warning of the material risks of the operation was a necessary condition of the harm he suffered. He also submitted that s 5D(1)(b) was satisfied as it was appropriate for the scope of the respondent's liability to extend to the harm so caused.

74 Section 5D is relatively recent legislation and there is at this point little High Court authority as to its scope and application and there is no authority on the application of s 5D in a case such as the present. There also appears to be scant consideration in the case law generally of the particular issue of causation that arises here.

The case law

75 The Court was not referred to any Australian case law directly on point (even on the non-statutory test for causation) and was not referred to any overseas authority. The appellant's approach was to take existing High Court authority in failure to warn cases as building blocks to demonstrate, through the interrelationship between the elements of the cause of the action in tort: duty, breach, causation, harm and damage, why and how the trial judge erred in his causation finding. Cases in New South Wales, the United Kingdom and the United States, which from the Court's researches are relevant to the specific question of causation in issue in this case, are also discussed below. The High Court authorities upon which the appellant relied are discussed first.

Rogers v Whitaker

76 As has already been indicated, the appellant's commencing point was with the scope and the content of the duty of care of a medical practitioner in a failure to warn case, which he submitted was a "single comprehensive duty" to take reasonable care: see Rogers v Whitaker. In that case, the plurality (Mason CJ, Brennan, Dawson, Toohey and McHugh JJ) stated, at 493, that the duty of care was not to be approached on the basis of an "artificial division or itemization of specific, individual duties, carved out of the overall duty of care". Rather:

"The duty of a medical practitioner to exercise reasonable care and skill in the provision of professional advice and treatment is a single comprehensive duty."

77 Their Honours also commented upon the emphasis in the United States authority to 'informed consent' as relevant to the action of trespass, noting that Australian law had not followed that path. Subject to the question of therapeutic privilege: see Canterbury v Spence 464 F 2d 772, 150 U.S.App.D.C. 263 (1972), which was not suggested in this case, the Australian position is that a failure to disclose risks inherent in medical procedures is founded in an action of negligence only. Their Honours stated that for the purposes of Australian law, the duty was to disclose material risks inherent in the procedure and that a risk was material if:

"... in the circumstances of the particular case, a reasonable person in the patient's position, if warned of the risk, would be likely to attach significance to it or if the medical practitioner is or should reasonably be aware that the particular patient, if warned of the risk, would be likely to attach significance to it. This duty is subject to the therapeutic privilege."

78 Gaudron J substantially agreed with the plurality judgment.

79 Gaudron J stated the test for ascertaining whether a risk was material in slightly different terms. However, as the test stated by the plurality has been consistently applied in the authorities and is essentially the same as the test that has evolved in overseas jurisdictions, it is not necessary to separately consider her Honour's formulation of the test of materiality, other than to note that she referred to Canterbury v Spence on this issue. That case is considered further below.

80 It should be noted that it was unnecessary for the Court in Rogers v Whitaker to deal with causation.

Chappel v Hart

81 In Chappel v Hart [1998] HCA 55; 195 CLR 232, there was an inherent risk in the operation performed on the plaintiff of perforation of the oesophagus which, if infection set in, could cause damage to the laryngeal nerve and other damage to the plaintiff's voice. The plaintiff was not warned of these risks, although the risk of infection in connection with perforation of the oesophagus was very small. It was found that if warned, the appellant would have deferred the operation and would have had it performed by a more experienced surgeon. The randomness of the likelihood of infection meant that it was unlikely that, if the operation was performed at some other time, the inherent risk of perforation in combination with infection would have come home.

82 The critical issue in Chappel v Hart was causation. The governing common law test required satisfaction of the "but for" test, but causation was otherwise determined in accordance with the "common sense" test of causation: see March v Stramare (E & M H) Pty Ltd [1991] HCA 12; 171 CLR 506. Gaudron, Gummow and Kirby JJ each held that the plaintiff's injury had been caused by the defendant's negligent failure to warn. The appellant relied upon the reasoning of Gummow J. However, reference should also be made to the reasoning of Gaudron J, to which Gummow J referred in the later decision of Rosenberg v Percival.

83 Gaudron J had regard to the connectivity between the duty of care and causation. Her Honour stated, at [7] 238:

"Questions of causation are not answered in a legal vacuum. Rather, they are answered in the legal framework in which they arise. For present purposes, that framework is the law of negligence. And in that framework, it is important to bear in mind that that body of law operates, if it operates at all, to assign a duty to take reasonable steps to prevent a foreseeable risk of harm of the kind in issue." (citation omitted)

84 Gummow J, after referring to the test in March v Stramare, referred to the judgment of Lord Hoffman in Environment Agency v Empress Car Co (Abertillery) Ltd [1999] 2 AC 22, where his Lordship stated that:

"... one cannot give a common sense answer to a question of causation for the purpose of attributing responsibility under some rule without knowing the purpose and scope of the rule ..."

Gummow J then observed, at [65] 256-257:

"The nature and purpose of a duty with the content established in Rogers v Whitaker concern the right of the patient to know of material risks which are involved in undergoing or forgoing certain treatment."

85 In Mrs Hart's case, the very risk of which the plaintiff should have been warned, materialised. It was a risk about which the plaintiff had made a specific enquiry and the evidence established that the potential consequences of damage to her voice were more significant to her than the statistical risk. The respondent doctor conceded that had the operation been performed at a different time, then, in all likelihood, the damage would not have occurred. Gummow J considered that those additional factors, combined with satisfaction of the "but for" test, were sufficient to establish causation in the particular case. As his Honour explained, at [68] 257:

"Here, the injury to Mrs Hart occurred within an area of foreseeable risk. In the absence of evidence that the breach had no effect or that the injury would have occurred even if Dr Chappel had warned her of the risk of injury to the laryngeal nerve and of the consequent risk of partial or total voice loss, the breach of duty will be taken to have caused the injury." (citations omitted)

86 Gummow J also referred, at [70] 258, to the place of logic and policy in the determination of the causation issue.

87 Although in dissent, the reasons of McHugh J are also relevant as his approach, on principle, was in accordance with the majority. His dissent was in his Honour's determination of the common sense and legal policy issues. His Honour accepted that the "but for " test had been satisfied. The failure to warn, in combination with other events, led to the perforation of the plaintiff's laryngeal nerve. However, as his Honour stated at [25] 243:

"The defendant's failure to warn, therefore, must be regarded as a cause of the plaintiff's injury unless either common sense or legal policy requires the conclusion that, for the purposes of this action, the failure is not to be regarded as a cause of the plaintiff's injury."

88 In his Honour's opinion, as a matter of logic, a defendant would only be held responsible where the defendant's conduct increased the risk of injury. His Honour then discussed the concept of material increase in risk, a matter not relevant to this case. However, it is useful to refer to his Honour's demonstration of that notion by reference to a different scenario in a negligent failure to warn of a landslide. That reference is relevant because of his Honour's acceptance that if a plaintiff would have abandoned a course of conduct, a failure to warn of a safer alternative route was an a fortiori example of a material increase in risk.

89 The present case is different from Chappel v Hart, which involved a failure to warn of a single risk that in fact materialised. This case involves a failure to warn of two material risks of the surgery, where only one materialised. However, Gaudron, Gummow and McHugh JJ recognised that the question of causation in the tort of negligence must be resolved having regard to the duty that has been breached. In that regard, whilst Gaudron J referred to the "duty to take care", Gummow J expressly referred to the nature and purpose of the duty in a failure to warn case as being that established in Rogers v Whitaker. This was a reference to the "a duty to warn of material risks", that duty being a "single comprehensive duty" not the itemisation of specific individual duties carved out of the overall duty to take care. The example given by McHugh J recognises that if there was an alternative, safer option available to a plaintiff, including of not going on the journey, which in this case is the equivalent of not having treatment at all, a failure to warn of danger would be causative of harm suffered.

Rosenberg v Percival

90 The appellant next referred to Rosenberg v Percival. That case involved a failure to warn of the risk of a particular complication of dental surgery, which caused severe and permanent pain.

91 Relevantly, for present purposes, Gleeson CJ observed, at [3] 348, that the issues of breach of duty and causation were related. This is an important observation for the appellant's argument, which is based upon a breach of a "single comprehensive duty" to warn of material risks. His Honour further observed, at [14] 441:

"Ordinary people live their lives surrounded by adverse contingencies that are foreseeable, in the sense that they are not far-fetched or fanciful. Transportation to a doctor's surgery may be accompanied by a foreseeable risk of serious injury in a motor vehicle accident, but such a risk is usually regarded as inconsequential. Even when surgical procedures are classified as elective, most people who undergo such procedures believe they have a serious reason for doing so; and doctors who recommend such procedures normally have the same belief. Thus, information about risk is being considered in the context of a communication between two people who have a common view that there is a serious reason in favour of the contemplated surgery. The more remote a contingency which a doctor is required to bring to the notice of a patient, the more difficult it may be for the patient to convince a court that the existence of the contingency would have caused the patient to decide against surgery."

92 In that case, his Honour categorised the adverse contingency as remote. His Honour noted that the trial judge had found the plaintiff's evidence unconvincing that, if warned, she would not have had the operation. His Honour reiterated that, in determining causation in cases of failure to warn, regard was to be had to the context before or at the time of the event, in which a particular contingency was to be evaluated. The necessity of doing so was to guard against the hindsight importance that a plaintiff, understandably, was likely to give to the failure to warn if an adverse consequence eventuated.

93 Gummow J, in noting the interrelationship of the issues of materiality and causation, referred to the observations of Gaudron J in Bennett v Minister of Community Welfare [1992] HCA 27; 176 CLR 408 at 422 where her Honour noted that "questions of the sufficiency of the precaution to avert the harm are inevitably subsumed in the finding that there was a duty". Gummow J continued, at [56] 452:

"It should be emphasised that a determination of whether the failure to warn of a risk was causative depends to a large extent on the definition or identification of the risk in question. Central to the identification of the risk are considerations of degree and severity. Those same considerations are also central to the question of whether the risk was material. If the Court comes to one view of those considerations when dealing with the materiality issue, the same view will direct the resolution of the causation issue."

94 In the context of the "identification of the risk", Gummow J, at [60] 453, stated that the duty that a medical practitioner owes to patient was "to warn ... of a material risk inherent in the proposed treatment". His Honour then turned to the question of the risk that was being spoken of in Rosenberg v Percival itself, noting that identification of the risk necessarily preceded the consideration of whether the risk was material. His Honour said, at [61] 453:

"Where the action is brought in negligence and the plaintiff is seeking compensation for an injury suffered, the relevant risk is the possibility that the proposed treatment will result in the injury that in fact occurred" (emphasis added)

95 In dealing with causation, his Honour explained the required connection between risk and injury, as involving two levels of inquiries. His Honour stated, at [83] 460:

"The question of whether a failure to warn of a material risk was causative of the plaintiff's injury involves two distinct levels of inquiry. At the first level, the risk must be related in a physical sense to the injury that was suffered. Thus, a medical practitioner will not be held liable for the failure to warn a patient of a material risk of damage to 'her laryngeal nerve', if the injury that eventuated resulted from a misapplication of anaesthetic. This is so despite the fact that the patient would not have had the treatment and therefore would not have suffered the injury from the misapplication of anaesthetic if the patient had been warned of the risk to 'her laryngeal nerve' [see Chappel v Hart at 257]. This can be seen as an example of a situation where the application of the 'but for' test would lead to an unacceptable result [see March v Stramare at 516]."

96 Gummow J had used the same example of the misapplication of the anaesthetic in Chappel v Hart at [66] 257. As had been explained by Mason CJ in March v Stramare at 516 (to which his Honour referred in the above passage), where an event:

"... secures the presence of the plaintiff at the place where and at the time when he or she is injured [the event] is not causally connected with the injury, unless the risk of the accident occurring at that time was greater."

97 Mason CJ accepted this as a recognised qualification to the application of the "but for" test: see Faulkner v Keffalinos [1970] 45 ALJR 80 at 86. See also the commentary by H L A Hart and Tony Honoré, Causation in the Law, 2nd ed (1985) at 122. In this context, Mason CJ commented, at 516-517, that the "but for" test "had to be tempered by the making of value judgments and the infusion of policy considerations": cf the contrary opinion that the "but for" test excluded such considerations: Weinrib, "A Step Forward in Factual Causation" (1975) 38 Modern Law Review 518, 530.

98 The second level of inquiry involved finding "a causal connection in the legal sense, between the failure to warn of the material risk and the occurrence of the injury": see at [84] 460. In this regard, Gummow J, at [85] 460-461, noted that the legal concept of causation is primarily concerned with attributing responsibility. He again referred to Lord Hoffmann's analysis in Environment Agency v Empress Car Co, at 29, that the answer to the question whether a person is liable for conduct "will depend upon the rule by which responsibility is being attributed". In the case of a claim of negligence, the relevant rule is identified within the framework of "a duty to take reasonable steps to prevent a foreseeable risk of harm of the kind in issue". In the same part of his reasoning, Gummow J endorsed the statement of Gaudron J in Chappel v Hart at [7] 238, set out at [83] above.

99 Earlier at [63](vi), Gummow J had referred to the statement in Rogers v Whitaker, that "the law should recognise that a doctor has a duty to warn a patient of a material risk inherent in the proposed procedure" (original emphasis). Then, at [86] 461, in the particular passage upon which the trial judge in this case relied, Gummow J said.

"In this case the purpose of the relevant rule is that stated in par (vi) of the extracts from the joint judgment in Rogers which have been set out above. This imposes an obligation upon medical practitioners adequately to warn their patients of the consequences of the treatment they are contemplating. If the medical practitioner should fail to warn the patient of a particular consequence and that consequence in fact eventuates then, subject to the question of materiality, the rule seeks to hold the medical practitioner liable for that consequence." (emphasis in trial judge's reasons)

100 His Honour next referred to Bennett v Minister of Community Welfare where Gaudron J said, at 420:

"[T]he issue is approached on the basis that 'when there is a duty to take a precaution against damage occurring to others through the default of third parties or through accident, breach of the duty may be regarded as materially causing or materially contributing to that damage, should it occur, subject of course to the question whether performance of the duty would have averted the harm."

101 His Honour then (still within [86] 461) summarised the position as follows:

"... causation, in the present kind of case, requires satisfaction of two criteria. The first criterion is a breach of the duty to warn of a material risk, that risk having eventuated and caused, in the physical sense, injury to the plaintiff. The second criterion is that, had the warning being given, the injury would have been averted, in the sense that the [plaintiff] would not have had the treatment in question."

102 The appellant's response contended that the remarks in Rosenberg v Percival were to be understood in the context that there was only one material risk of harm. In essence, the appellant's position was that linguistic focus on "that risk" or "that consequence" eventuating or materialising, did not mean that a failure to warn of two or more material risks, only one of which eventuated as in this case, could not, as a matter of legal principle, be causative of harm. It was the appellant's submission that to the extent that the trial judge had found otherwise, he erred.

103 The respondent's submissions emphasised first the subjective nature of the test in determining what the patient would have done if warned of the risk and secondly, the necessity for causation to be referrable to the risk that materialised. He relied, in particular, upon the approach of McHugh J in Rosenberg v Percival in the following passage:

"[25] It follows from the test being subjective that the tribunal of fact must always make a finding as to what this patient would have done if warned of the risk. In some cases where there is no direct evidence as to what the patient would have done, the judge may infer from the objective facts that the patient would not have undergone the procedure ...

(This passage must now be read subject to s 5D(3).)

[45] In terms of causation theory, the critical fact is whether the patient would have taken action - refusing to have the operation - that would have avoided the harm suffered. But that fact can only be determined by making an anterior finding as to what the patient would have decided to do, if given the relevant warning. It is not possible to find what the patient would have done without deciding, expressly or by necessary implication, what decision the patient would have made, if the proper warning had been given. If the court finds that the patient would have decided not to have the operation, it concludes that he or she would not have had the operation. What the patient would have decided and what the patient would have done are hypothetical questions. But one relates to a hypothetical mental state and the other to a hypothetical course of action." (emphasis added)

104 The respondent acknowledged that McHugh J was addressing his remarks to a case where there was "a risk of harm": see at [24] 443, but contended that his Honour's approach was of general application, that is, the question of causation was determined solely by reference to the risk that came home.

The other authorities

New South Wales authority

Ellis v Wallsend District Hospital

105 Prior to the High Court authorities discussed above, the question of causation in a failure to warn case had been considered by this Court in Ellis v Wallsend District Hospital (1989) 17 NSWLR 553.

106 In that case, the plaintiff brought proceedings against the defendant hospital in circumstances where, six days after she underwent surgery performed by a visiting honorary surgeon on her neck, she developed quadriplegia. The plaintiff brought her claim against the hospital only on the basis that it owed her a non-delegable duty of care which extended to the medical services provided by an honorary medical officer to a private patient. Alternatively, she alleged that the hospital was vicariously liable for the negligence of the honorary surgeon who performed the operation.

107 The plaintiff was only warned of the risk of some slight numbness in her right hand consequent upon the operation. However, the surgery carried with it a risk of paralysis, because of the close proximity of the operation site to the spinal cord. That risk was small, but not fanciful. There was also substantial risk that the surgery might not relieve her neck pain. In fact, there was only a 30 per cent chance of success of relief. The surgeon was found to be negligent in failing to warn the plaintiff of those two risks. However, the trial judge concluded that the plaintiff would not have refused to have the operation even if warned of the slight risk of paralysis. The trial judge also held that there was no evidence that the plaintiff would have refused the operation had she been warned that there was only a 30 per cent chance of success in respect of long-term pain relief. He dismissed the plaintiff's claim.

108 On appeal, the plaintiff was successful in establishing causation on the failure to warn case, although not ultimately successful in her claim against the defendant hospital, which was found not to owe her a non-delegable duty, nor to be vicariously liable for the honorary surgeon's negligence. In issue on the question of what course the plaintiff would have taken had she been adequately warned of the risks of the operation, was whether the trial judge had correctly assessed the evidence as to the plaintiff's subjective intention.

109 Kirby P (who would have allowed the appeal) agreed with Samuels JA on the question of causation. In particular, Kirby P observed, at 561, that the plaintiff was entitled to be given a candid and balanced statement of the risks. As his Honour said, at 561, "the bigger the devastation of the possible risk, the greater is the obligation to lay it before the patient". His Honour continued:

"An operation with a very high success rate and a very low risk of paralysis may, rationally, be accepted much more readily than one where the prospects of success were more circumscribed, though the risk of paralysis was still slight."

110 Samuels JA, with whom Meagher JA agreed, stated, at 590, that the trial judge:

"... did not give any attention to the possible subjective response which the [plaintiff] might have made had the information conveyed to her contained both a warning about possible paralysis and an accurate assessment of the likely prospects of success. This is curious ... because he found that [the surgeon's] negligence involved failure to warn about both these matters ... he took this course, I would judge, because of the way in which he eliminated from consideration the possible influence of the low rate of statistical success. But, in my respectful opinion, he was not only bound to consider that matter alone from a subjective standpoint, but bound also to consider it from the same standpoint as one of two combined elements in the warning which the appellant should have received."

111 Ellis v Wallsend District Hospital is directly on point to the issue raised in the present case. However, it is not binding on this Court, as it was decided in accordance with common law principles and not under the statute. In addition, their Honour's comments were also strictly obiter. However, the Court's reasoning on the need to consider the combined risks of which a warning was required is persuasive as to the matters that may be relevant when determining whether it is "appropriate for the scope of a negligent person's liability to extend to the harm so caused" for the purposes of s 5D(1)(b). Their Honours' reasoning is also consonant with the interrelationship of duty and causation, established in the High Court authorities, and which has not been abrogated by the statutory provisions.

The UK authorities

Chester v Afshar

112 In Chester v Afshar [2004] UKHL 41; [2005] 1 AC 134, the plaintiff had not been warned of the risk of cauda equina syndrome, which had about 1-2 per cent chance of occurrence. That risk came home.

113 The plaintiff's claim was upheld in circumstances where the majority of their Lordships concluded that the plaintiff had not established, on conventional principles, that her injury had been caused by the medical practitioner's failure to warn of the risk of the serious condition of cauda equina syndrome. The plaintiff had not adduced evidence as to what she would have done if warned of the risk. The headnote sufficiently summarises the reasoning of the majority for present purposes:

"[The issue of causation was to be addressed] by reference to the scope of the doctor's duty, namely, to advise his patient of the disadvantages or dangers of the treatment he proposed; that such a duty was closely connected with the need for the patient's consent and was central to her right to exercise an informed choice as to whether and, if so, when and from whom to receive treatment; that, since the injury she sustained was within the scope of the defendant's duty to warn and was the result of the risk of which she was entitled to be warned when he obtained her consent to the operation in which it occurred, the injury was to be regarded as having been caused by the defendant's breach of that duty; and that, accordingly, justice required a narrow modification of traditional causation principles to vindicate the claimant's right of choice and to provide a remedy for the breach." (emphases added)

114 The reasoning of the majority is relevant insofar as it refers to the interrelationship of the scope of the duty and causation. Lord Bingham and Lord Hoffmann dissented. Lord Bingham noted that if the plaintiff would not have undergone the surgery if warned of its inherent risks, she would, on conventional principles, have been entitled to recover damages. However, in the absence of a finding to that effect, the plaintiff had not established factual causation on the application of the "but for" test. In his Lordship's view, a defendant should not be liable when it had not been established that the defendant's conduct had worsened the physical condition of the plaintiff: see Chappel v Hart per McHugh J.

115 Lord Hoffmann, at [31], considered that the relevant question on causation was whether the plaintiff would have taken the opportunity to avoid or reduce the risk, not whether the plaintiff would have changed the scenario. This was decisive of the outcome on his Lordship's view, because the trial judge had found that the risk would have been precisely the same whether the operation was performed then, or later, by the same or a different surgeon. His Lordship also agreed with the reasons of Lord Bingham, and thus with the judgment of McHugh J.

116 Apart from Ellis v Wallsend District Hospital, the authorities considered thus far involved a failure to warn of a specific risk, which materialised. This case involves a failure to warn of material risks, only one of which materialised. That circumstance arose for determination in Moyes v Lothian Health Board 1990 S.L.T. 444 where the plaintiff suffered a stroke in the course of an angiogram. Her claim against the defendant included the alleged negligence of the neurological surgeon, who performed the angiography, in failing to warn her of the aggravated risk of a stroke occasioned by her hypersensitivity to the contrast medium used in the procedure and by her previous history of migraine.

117 The plaintiff's action failed as she was unable to prove a previous hypersensitive reaction or that either hypersensitivity or allergy had caused her stroke. However, in commenting on the causation question in a failure to warn case, Lord Caplan stated, obiter, at 447:

"The ordinary person who has to consider whether or not to have an operation is not interested in the exact pathological genesis of the various complications which can occur but rather in the nature and extent of the risk. The patient would want to know what chance there was of the operation going wrong and if it did what would happen ... It is perfectly conceivable that a patient might be prepared to accept the risk of one in 100 but not be prepared to face up to a risk of one in 20. If a doctor contrary to established practice failed to warn the patient of the four special risks but did warn the patient of the standard risk and then the patient suffered complication caused physiologically by the standard risk factor rather by one or other of the four special risks factors I do not think the doctor should escape the consequences of not having warned the patient of the added risks which that patient was exposed to. A patient might well with perfect reason consider that if there were five risk factors rather than one then the chance of one or other of these factors materialising was much greater. The coincidence that the damage which occurred was due to the particular factor in respect of which a warning was given does not alter the fact that the patient was not properly warned of the total risks inherent in the operation and thus could not make an informed decision as to whether or not to go through with it. In the example I give, by going through an operation with five risk factors rather than one the patient was exposed to a degree of risk materially in excess of what the patient had been warned about and was prepared to accept. If he had been given due warning he would have not risked suffering adverse complication from that particular operation and the fact that such complication occurred is causal connection enough to found a claim against the doctor."

The Canadian authorities

118 There is also support for the appellant's argument in the Canadian authorities, although those authorities must be read with care, having regard to that jurisdiction's acceptance of the objective test in determining what a plaintiff would have done if warned. It is sufficient to consider the well-known authority, Reibl v Hughes [1980] 2 S.C.R. 880, 14 C.C.L.T.1, 114 D.L.R. (3d) 1, 33 N.R. 361, J.E. 80-894.

Reibl v Hughes

119 In Reibl v Hughes, the Supreme Court identified the relevant duty of care of a surgeon to a patient "to make disclosure ... of ... all material risks attending the surgery which is recommended": see Hopp v Lepp [1980] 4 W.W.R. 645, 13 C.C.L.T. 66, 32 N.R. 145, 22 A.R. 361. The particular risks attending the surgery in that case were of stroke, paralysis and death. There were risks of stroke and death if the surgery was not performed. The Court was concerned with the question of how specific the information should be to enable the patient to make an "informed" choice between surgery and no surgery. The Court considered that the term "informed consent" should be abandoned when the question involved the duty of disclosure of material risks and that cases in trespass should be restricted to where there was no consent at all. This is in accord with the Australian authority that the relevant cause of action for failure to disclose is negligence, not trespass: see Rogers v Whitaker above at [77].

120 The Supreme Court held that the trial judge had correctly found that the surgeon had breached his duty of care to the patient. He had failed to give the patient an adequate disclosure of the risk of death or paralysis attendant upon the surgery itself and had also failed to inform the patient that the operation would not alleviate his headaches and hypertension, about which he had been concerned. On the question of causation, the Supreme Court held that a reasonable person in the plaintiff's position (that is, on the application of an objective test) would have refused the surgery, having regard to the combination of circumstances and, in particular, had he been informed of the particular serious risks of the surgery and of the fact it would not have cured his headaches and hypertension.

The American authorities

Canterbury v Spence

121 The starting point for the American case law is Canterbury v Spence. That case is authority in the United States for the principle that the question of what a plaintiff would have done if adequately warned of the risks of treatment is to be determined on an objective basis. The approach in Canterbury v Spence on this question has been expressly rejected in Australia in favour of a subjective test. Section 5D(3), which governs this case also provides for a subjective test. Relevantly for the question in issue in this case, however, was the US Court of Appeals, District of Columbia Circuit approach to causation in cases of a failure to warn of material risks.

122 The case, which was a single risk case, concerned a claim against a surgeon in trespass and negligence for a failure to warn of a 1 per cent risk of paralysis in respect of a laminectomy. Approximately one day after surgery, the plaintiff fell from his hospital bed. Some hours later, the plaintiff commenced to suffer from paralysis from the waist down. A second operation was performed to release pressure from the spinal cord, however, the plaintiff did not fully recover his mobility.

123 There was a directed verdict at first instance in favour of the surgeon, on the basis that there was no evidence of negligence either in the diagnosis of the plaintiff's condition or in the performance of the surgery. The trial judge did not deal with the alleged negligence based on the surgeon's failure to warn of the risk of paralysis. In that regard, the Court of Appeals recognised the existence of a cause of action in negligence where a physician had failed to provide an adequate warning of the risks involved in any proposed treatment, independently of a claim in trespass based on an absence of informed consent. The matter was remitted for a new trial on all issues, other than the claim in trespass which was statute barred.

124 Insofar as the claim was based in the failure to warn, the Court of Appeals defined the scope of the duty as being the disclosure of material risks. The Court explained "material risk", at [22], in the following terms:

"[a] risk is thus material when a reasonable person, in what the physician knows or should know to be the patient's position, would be likely to attach significance to the risk or cluster of risks in deciding whether or not to forego the proposed therapy." (emphasis added)

125 The Court of Appeals noted, at [24]-[25], that a medical practitioner was not required to disclose risks that had no apparent materiality to the patient's decision on therapy. However, the Court of Appeals noted it did not subscribe to the view that only risks that would cause a patient to forego treatment were required to be disclosed:

"... for such a principle ignores the possibility that while a single risk might not have that effect, two or more might do so."

126 The Court of Appeals then dealt with the issue of causation in the following terms:

"[30] ... An unrevealed risk that should have been known must materialize, for otherwise the omission, however unpardonable, is legally without consequence. Occurrence of the risk must be harmful to the patient, for negligence unrelated to injury is nonactionable. And, as in malpractice actions generally, there must be a causal relationship between the physician's failure to adequately divulge and damage to the patient.

[31] A causal connection exists when, but only when, disclosure of significant risks incidental to treatment would have resulted in a decision against it." (footnotes omitted)

127 These passages, in their terms, support the proposition that it is only the risk that came home that is relevant to causation. However, it has been otherwise interpreted in the United States, given the requirement to establish "proximate cause".

Downer v Veilleux

128 In Downer v Veilleux 322 A 2d 82 (Me. 1974) the Supreme Judicial Court of Maine was concerned, inter alia, with the question of causation where there had been an alleged failure to adequately disclose the various procedures available to treat the fractures the plaintiff sustained in a motor vehicle accident. The Court held that the proof of "proximate cause" required establishing that the non-disclosed risk, which should have been made known, had materialised. The Court stated, at [12], that absent occurrence of the undisclosed risk, the doctor's omission was legally inconsequential. This statement was firmly based on the United States test of "proximate cause". The Court had noted, at [11], that:

"As in the case of any breach of a legal duty, the plaintiff must, as in malpractice actions generally, prove a proximate causal relationship between the physician's failure to adequately inform and injury to the plaintiff."

129 The Court continued, at [12]:

"Proof of proximate cause in such cases requires, initially, a showing that the unrevealed risk which should have been made known has materialized. Absent occurrence of the undisclosed risk, the doctor's omission is legally inconsequential."

130 Canterbury v Spence and Downer v Veilleux are accepted authority in the United States for the proposition that an undisclosed risk must materialise in order for causation to be established: Cochran v Wyeth 3 A 3d 673 (Pa.Super, 2010). Cochran v Wyeth has a closer analogy to this case. The case involved a claim by a plaintiff against a drug company for inadequate disclosure of the side effects of a certain drug. The plaintiff suffered a side effect that had been disclosed. She asserted, however, that the drug company had failed to disclose another side effect, such that if disclosed, her medical practitioner would not have prescribed the drug for her.

131 The Court observed, at 28, that in informed consent cases it appeared to be well settled that "the non-disclosed risk must manifest itself into actual injury in order for a plaintiff to establish proximate causation". The Court held that a plaintiff would fail to establish "proximate causation" where the non-disclosed risk failed to materialise in an injury. The Court stated, at 30, that:

"... before a plaintiff can prove that a non-disclosed risk would have altered the physician's decision to prescribe a drug, the plaintiff must first demonstrate that he/she suffered from the precise injury that the manufacturer failed to disclose."

132 In adopting this approach, the Court observed that Canterbury v Spence and Downer v Veilleux had been uniformly accepted by high courts of other jurisdictions in the United States. The Court further stated that it had been unable to locate any authority that had refused to adopt the "proximate causation" principle enunciated in those two cases.

133 It should be noted that integral to the decision was that the tort of informed consent corresponded with the tort of failure to warn, so that the same test of "proximate causation" applied to both causes of action.

134 The Court commented that a similar test had been imposed in claims in cases of fraudulent omissions or misrepresentations, stating, at 28 footnote 2, that in that area of jurisprudence:

"These cases hold that in order to be compensable, the non-disclosed risk of misrepresented fact must materialize into an injury that is specifically related in scope to the peculiar nature of the omission or misrepresentation."

135 Even making allowance for the objective test for determining what a plaintiff would have done if warned, these United States cases do not support the appellant's case. However, I do not consider them to be persuasive in the present context because of the different test of causation, that is, the test of "proximate causation" that applies in American law. That is not the test for the purposes of s 5D: see s 5D(3).

Should the appeal be allowed?

136 This case involved a duty to give the appellant an adequate warning of the material risks of undergoing the surgery. The appellant contended there were two material risks: the neurapraxia, which the trial judge held was a material risk, and the 5 per cent risk of paralysis. The judge made no finding as to the materiality of this risk, although for the reasons I have given, there may be no real dispute about that.

137 Only one of the risks, the neurapraxia, eventuated. The appeal directly raised the question whether, in determining causation in a case of failure to warn of material risks, the only relevant risk is the one that eventuated. Or is it sufficient that the harm suffered is within the area of foreseeable harm, and it is determined that the patient would not have had the operation if warned of a material risk that did not come home.

138 That factual circumstance did not arise for consideration in the trilogy of High Court authority: Rogers v Whitaker, Chappel v Hart and Rosenberg v Percival, in which the parties respectively sought to find the principle which should govern such a case. In my opinion, the references in those cases to the undisclosed risk materialising does not preclude, as a matter of principle, the existence of a causative link to the harm suffered, when an undisclosed risk, being one of two or more material risks, does not materialise.

139 In my opinion, the statements of Gummow J in Rosenberg v Percival, in particular at [86] 461, which led the trial judge to a contrary conclusion, have to be read in the context of the factual circumstances with which the Court was concerned. Paragraph [61] 453 of Gummow J's reasons is also relevant in understanding his Honour's reasons as a whole.

140 At [61] 455, his Honour was dealing with the "identification of the risk". In that context, his Honour stated, at [64], that the "relevant risk" was:

"... real and foreseeable ... [The] character of the injury or the precise sequence of events leading to the injury need not be foreseeable ... even if the extent of the injury was greater than expected." (at [64])

141 This principle derives from Hughes v Lord Advocate [1963] UKHL 1; [1963] AC 837 where liability was held to be established in circumstances where the risk of fire was foreseeable although an explosion (which occurred) was not. That is a different question from whether a relevant, material risk was causative of harm. That was the issue with which his Honour was concerned at [86] 461 and which, as I have explained, he dealt with by reference to the relevant rule of responsibility. In other words, that was his Honour's approach to the principle that governed the determination of the causation question.

142 His Honour's statement that a "failure to warn of a consequence and that consequence [eventuating]" was, in my opinion, focussed upon the particular factual circumstances in that case, namely a failure to warn of a single material risk. Any different interpretation would undermine the two basal concepts upon which his reasoning proceeds, namely, the determination of a defendant's liability having regard to the relevant rule of responsibility and the interrelationship of causation with the nature and scope of the relevant duty. The relevance of those concepts to the application of s 5D(1) is dealt with below.

143 Neither party referred to Ellis v Wallsend District Hospital, nor to any overseas authorities discussed. As I have already indicated, the reasoning in Ellis v Wallsend District Hospital is persuasive in relation to the causation issue that arises in this case. The English and Canadian case law discussed above is also supportive of the proposition that there may be a causative link to harm suffered, even though one of two or more material risks does not eventuate. None of those cases were decided under the statutory test of causation that governs this case. However, I do not consider that undermines their persuasiveness. They all recognise the interrelationship of the nature and scope of the duty of care to disclose material risks inherent in a medical procedure and causation.

144 In my opinion, the statutory content of the causation question prescribed by s 5D(1) does not negate or modify this relationship, except to the extent that there may be policy considerations that impact upon the s 5(1)(b) question that compel a contrary conclusion.

145 The Civil Liability Act, Pt 1B relates to claims in negligence: s 5A(1). Negligence is defined as "a failure to exercise reasonable care and skill": s 5. Apart from the definition, the statute does not, nor could it prescribe the nature, scope or content of the duty of care in a particular case. Accordingly, when a court is concerned to determine the nature, scope and content of the duty of care, it is concerned with the notion described by Lord Hoffmann in Environment Agency v Empress Car Co as the relevant rule of responsibility. The notion of the relevant rule of responsibility has found acceptance in express terms in Australia including, but not only, in the cases to which I have referred. In this regard, see also: Travel Compensation Fund v Tambree [2005] HCA 69, 224 CLR 627; Pledge v RTA [2004] HCA 13; 205 ALR 56; Cattanach v Melchior [2003] HCA 38; 215 CLR 1; Tame v NSW [2002] HCA 35; 211 CLR 317; Modbury Triangle Shopping Centre v Anzil [2000] HCA 61; 205 CLR 254. The same notion was expressed by Gaudron J in Chappel v Hart at [7] 238.

146 The statute does specify what is involved in breach and the considerations relevant, non-exclusively, to that determination. Likewise, the statute specifies the elements of causation referred to as the "but for" test and the "scope of liability" rule. It is likely that the statutory test is conceptually different from the common law test in March v Stramare but, in any event, it is the statutory language that governs: see Adeels Palace Pty Ltd v Moubarak; Adeels Palace Pty Ltd v Bou Najem [2009] HCA 48; 239 CLR 420.

147 However, the prescription of the statutory elements of causation has not abrogated the necessary interrelationship of and connection between the duty of care, its nature and scope and causation. On the contrary, I am of the opinion that the interrelationship plays an integral role in the determination of the "scope of liability" element of causation. Accordingly, in my opinion, the statements of Gaudron J at [7] 238 and Gummow J at [65] 256-257 in Chappel v Hart and Gummow J's further comments in Rosenberg v Percival at [86], continue to apply to questions of causation under the statute.

148 As those statements apply to a case of a failure to warn, it means that the causation question has to be determined having regard to the content of the duty, namely a duty to warn of material risks. Accordingly, where there is more than one material risk, and a finding is made that a plaintiff would not have undergone surgery if warned of other material risks, it is difficult to see reasons in logic or policy why a negligent doctor should not be liable notwithstanding that a different risk eventuated.

149 In every case however, the determination is a factual one. A court might readily conclude that where a risk, although material, has relatively minor consequences, it would not be appropriate for the scope of the defendant's negligent failure to warn of that risk to extend to the different harm that in fact eventuated. A more difficult factual question might arise where the failure is to warn of a different material risk with relatively serious consequences but with a low a chance of occurrence.

150 In this case, the failure to warn was of a material risk with very serious consequences should it occur and with a high risk of occurrence. If in such a case, it were to be found that a plaintiff would not have undergone surgery if warned of the risk, then I consider that it is appropriate that the scope of the defendant's liability extend to the harm in fact caused.

151 A case of failure to warn of more than one material risk is different from the example of the harm suffered whilst a patient was under an anaesthetic, to which Gummow J referred in Rosenberg v Percival. It is doubtful whether harm of that type would satisfy the "but for" test. It might also be arguable that such a circumstance constituted a novus actus. By contrast, the connection between the nature and scope of the duty, and what the plaintiff would have done if there had been no breach, are sufficiently and logically connected for it to be appropriate for the scope of the defendant's to extend to the harm in fact suffered. In my opinion, the trial judge erred in finding that the only potentially relevant risk was the neurapraxia.

Conclusion

152 As I have stated, the trial judge did not resolve the factual dispute as to whether the respondent disclosed the risk of a 5 per cent catastrophic outcome. That is a necessary finding if, on the appellant's approach to the issue of causation, his case is to succeed. The Court was invited to make that finding if it came to the conclusion that his Honour erred in finding, at [88], that the only relevant warning was of the risk of bilateral femoral neurapraxia. However, whether or not the warning of paralysis was given involves questions of credit. Although his Honour referred to the credit of the witnesses, his comments are not of such a nature that the Court could conclude that the evidence of the appellant and his wife was to be preferred to the evidence of the respondent, or vice versa.

153 The Court was also invited to make findings as to whether, if warned, the appellant would have had the operation. The parties' submissions on that question are to be found at [68]-[69] above. However, that finding also involves questions of credit and for the same reasons, it is not appropriate for the Court to engage in a fact finding task of this nature.

154 It follows, in my opinion, that the appeal should be allowed.

155 I propose the following orders:

1. Appeal allowed;

2. Set aside the verdict for the respondent and the costs order made by the trial judge;

3. Remit the matter for rehearing;

4. Order that the costs of the original trial be in the determination of the judge on the retrial (or abide the outcome of the retrial);

5. Order the respondent to pay the appellant's cost of the appeal. The respondent to have a certificate under the Suitors' Fund Act 1951 if qualified.

156 BASTEN JA: It is curious that the circumstances of this case have not previously arisen, so far as the Court is aware. The appellant, Mr Ian Wallace, sought medical assistance in relation to a condition in his lumbar spine. He was offered surgery. Because he was significantly overweight, the surgery was likely to be lengthy and there was a risk that he would sustain transient local nerve damage in his thighs (described as bilateral femoral neurapraxia). The risk materialised, although the condition had entirely resolved by the time of the trial. At a consultation with the respondent, Dr Kam, before the operation, the appellant was given important information in respect of the procedure and its potential for success and the likely circumstances of rehabilitation, but was not advised of that particular risk. The primary judge (Harrison J) held that he should have been, but that, if he had been, he would nevertheless have proceeded with the operation. Accordingly, the judge held that the failure to warn did not constitute a relevant cause of the harm and dismissed the claim: Wallace v Ramsay Health Care Ltd [2010] NSWSC 518.

157 The operation also carried with it a 5% risk of a catastrophic outcome. The appellant said he was not warned of that either. However, because it did not eventuate, the trial judge held that any failure to warn of a risk of a catastrophic outcome was causally irrelevant: at [88]. The appellant challenged that reasoning, contending that had he been so warned, he would not have had the operation, and would thus not have suffered the transient local nerve damage. Because the judge considered the failure to warn of a catastrophic outcome was causally irrelevant, he made no findings as to whether the practitioner did fail to provide adequate advice as to that risk and as to the likely response of the appellant, if warned.

158 One reason why questions of causation give rise to difficult issues in this area is that there is no negligent mistreatment causing harm, the harm being the materialisation of a risk inherent in the procedure, even when carried out with all due skill and care. The failure to warn of attendant risks is not itself a direct cause of the harm suffered: it is not a breach of any duty on the part of the practitioner to carry out the procedure with due skill and care, but rather depends upon a legal requirement that it be the patient who ultimately determines (absent an emergency) whether the procedure is undertaken or not.

159 The right to recover damages in the present case was put, in part, on the basis of upholding the autonomy of the patient to determine whether or not to have the procedure. That contention is, however, too broadly stated. Like the "somewhat amorphous phrase 'informed consent'", the concept is apt to mislead: see Rogers v Whitaker [1992] HCA 58; 175 CLR 479 at 490 (Mason CJ, Brennan, Dawson, Toohey and McHugh JJ). As the judgment continued:

"Anglo-Australian law has rightly taken the view that an allegation that the risks inherent in a medical procedure have not been disclosed to the patient can only found an action in negligence and not in trespass; the consent necessary to negative the offence of battery is satisfied by the patient being advised in broad terms of the nature of the procedure to be performed."

160 This passage has been identified as a warning against the uncritical use of concepts "which ought to be valuable currency, but which are susceptible to rhetorical inflation": Rosenberg v Percival [2001] HCA 18; 205 CLR 434 at [9] (Gleeson CJ).

161 The appellant pressed upon the Court the importance of the statement in Rogers v Whitaker that "[t]he duty of a medical practitioner to exercise reasonable care and skill in the provision of professional advice and treatment is a single comprehensive duty": at 489. However, the adoption of that language was curious: the phrase "a single comprehensive duty" derived from the speech of Lord Diplock in Sidaway v Governors of Bethlem Royal Hospital [1985] AC 871, in which he (as one of the majority) held that the Bolam principle (requiring a standard fixed by reference to the views as to proper practice held by a responsible body of medical opinion) applied with respect to that element of the duty concerned with the provision of information and advice. The High Court rejected that approach, preferring the dissenting view of Lord Scarman in Sidaway, at 488-489; see also Gaudron J at 492. As the joint judgment explained, there is "a fundamental difference between, on the one hand, diagnosis and treatment and, on the other hand, the provision of advice or information to a patient": at 489. The consequence of the difference, identified in that case, was that the content of the duty of disclosure was not a matter to be determined by practice within the medical profession, but was to be objectively determined by a court, by reference to the state of relevant medical knowledge. The test was identified in the following terms (at 490):

"The law should recognize that a doctor has a duty to warn a patient of a material risk inherent in the proposed treatment; a risk is material if, in the circumstances of the particular case, a reasonable person in the patient's position, if warned of the risk, would be likely to attach significance to it or if the medical practitioner is or should reasonably be aware that the particular patient, if warned of the risk, would be likely to attach significance to it."

162 A differential approach to elements of professional negligence is now required by ss 5O and 5P of the Civil Liability Act 2002 (NSW). Courts are to approach the standard or content of the duty by reference to a national standard of peer professional opinion as to competent practice, if widely accepted and not "irrational": s 5O. However, that approach does not apply to the duty to give "a warning, advice or other information in respect of the risk of death or injury": s 5P. In that area the general law, as reflected in Rogers v Whitaker, remains applicable. Similarly, the provisions of the Civil Liability Act dealing with warnings of obvious risks of death or personal injury do not apply with respect to professional services: s 5H.

163 The Civil Liability Act provides that a determination that negligence caused particular harm comprises two elements: s 5D(1), chapeau, set out at [70] above. It is to be read as requiring that unless the plaintiff proves the relevant facts (s 5E) and the court is satisfied as to the other elements, there can be no finding of causation. The apparent purpose of s 5D(1) is to ensure that physical and policy elements of causation are identified and addressed separately. That purpose is immediately muddied, however, by s 5D(2), which allows for an affirmative finding of causation, absent satisfaction of the "necessary condition" test of physical or factual causation, if "established principles" permit such a finding. Although sub-s (2) does not use the phrase "scope of liability" used in sub-s (1), it requires the court to consider "(amongst other relevant things) whether or not and why responsibility for the harm should be imposed on the negligent party", which is the language used in defining the "scope of liability" inquiry: s 5D(4). In short, the 'policy' considerations both limit the area within which the counterfactual inquiry results in liability and, "in an exceptional case", permit liability where the counterfactual inquiry is not satisfied.

164 In truth, any attempt to treat elements of causation as entirely separate and distinct is doomed to fail in contestable cases, as is a rigid compartmentalisation of duty, breach and causation: see Rosenberg at [3] (Gleeson CJ); [56] (Gummow J), dealing with "materiality" of risk and causation. The scope and content of the duty to warn depends on the identification, with as much precision as the circumstances permit, of a foreseeable adverse consequence. It is only when that exercise is undertaken, on the basis of medical knowledge reasonably available to the practitioner at the time of the consultation, that the question of "materiality" can be addressed and, if the risk be found to be material, the likely consequence for the particular patient of being given the appropriate advice can be determined: Rosenberg at [60]-[61], [66]-[69] and [75]-[80] (Gummow J).

165 The facts of Rosenberg have been explained by Beazley JA and need not be repeated here. Importantly, in dealing with the question of causation, Gummow J stated at [83]:

"The question of whether a failure to warn of a material risk was causative of the plaintiff's injury involves two distinct levels of inquiry. At the first level, the risk must be related in a physical sense to the injury that was suffered. Thus, a medical practitioner will not be held liable for the failure to warn a patient of a material risk of damage to 'her laryngeal nerve', if the injury that eventuated resulted from a misapplication of anaesthetic. This is so despite the fact that the patient would not have had the treatment and therefore would not have suffered the injury from the misapplication of anaesthetic if the patient had been warned of the risk to 'her laryngeal nerve'. This can be seen as an example of a situation where the application of the 'but for' test would lead to an unacceptable result."

166 Gummow J noted, in relation to "the second level", that a failure to warn of a risk cannot be said to "cause" an injury in the same way that one speaks of causation in respect of careless conduct in carrying out the operation. The second level requires identification of the purpose for which a causal relationship is being assessed, namely the attribution of responsibility for the harm. At [86], he continued:

"[The relevant rule] imposes an obligation upon medical practitioners adequately to warn their patients of the consequences of the treatment they are contemplating. If the medical practitioner should fail to warn the patient of a particular consequence and that consequence in fact eventuates then, subject to the question of materiality, the rule seeks to hold the medical practitioner liable for that consequence."

167 The reference to warning of "a particular consequence", followed by the condition that "that consequence in fact eventuates" is not ambiguous. Nor is it to be dismissed as an incautious or inaccurate use of language.

168 The US cases referred to by Beazley JA are to similar effect. The results in those cases are not to be ignored because the judges used the language of "proximate cause" not presently in vogue in Australia. That phrase may be traced to Sir Francis Bacon: Michael S Moore, Causation and Responsibility: An Essay in Law, Morals and Metaphysics (OUP, 2010), p 101. It is, like "scope of liability", a label to describe the boundaries of liability derived from the purposes or policies of the law. It does not dictate one conclusion rather than another.

169 The arguments in favour of permitting recovery in this case, subject to relevant facts being found, are broadly twofold. One is that the duty to warn should not be subdivided because the decision to undergo treatment is a single decision made by assessing all the appropriate information: it cannot sensibly be partitioned. A second, though related, argument is that the risks were not entirely distinct, as were the risk of severing a nerve and a problem with anaesthesia, in the example used by Gummow J in Chappel v Hart [1998] HCA 55; 195 CLR 232 at [66] and in Rosenberg at [83].

170 These arguments clearly turn on matters of degree and do not rely on watertight legal categorisation. Thus, in respect of the first argument, there is a close correlation between the tasks of assessing the materiality of a risk and the causal relationship with the harm. Neither can be resolved without careful attention to the particular risk as identified in the medical literature, the manner in which it should be described to the patient and the way in which it will be understood and assessed by the patient. Although the patient has but one decision to make, the factors to be placed into the balance in making that decision (in the somewhat idealised paradigm adopted by the law) are separate and each has its own weight.

171 The correlation between the tasks of assessing the materiality of a risk and the causal relationship with the harm is also close in a practical sense. Absent some subjective element known to (or which should have been apprehended by) the practitioner, "materiality" involves an objective test of assessing the likely significance of a particular risk, but by reference to a reasonable person in the plaintiff's position. The test of causation is said to be subjective, namely, asking whether this patient would have declined to undergo the treatment. However, given the inadmissibility of any statement by the patient after suffering the harm, and favourable to his or her interests, as to what he or she would have had done had the appropriate warning been given (s 5D(3)(b)), the difference between the two tasks is diminished. At least that is so in a case where the plaintiff has exhibited no specific concern before the operation as to the risks involved. Yet the materiality analysis, relevant to the identification of breach, does require separate assessment of each risk as to which it is said a warning should have been given. A trial judge could accept that, although the warning with respect to a specific risk would not have been significant to this patient, objectively it should have been given. Such a conclusion must carry with it a strong implication in relation to the possible causal connection with the harm in fact suffered.

172 In respect of the second argument, it is not self-evident that the two risks in question were closely associated. The catastrophic risk of paralysis was inherent in the site and nature of the procedure, close to the spinal column. It could have a close connection with the skill and care exercised by the surgeon in carrying out the operation. By contrast, the bilateral femoral neurapraxia, which materialised, arose from the fact that the patient was required to lie prone for a significant period. The distinction between the two is not far removed from the examples relied on by Gummow J, being the possible injury to the laryngeal nerve and the risk of misapplication of the anaesthetic.

173 As a matter of principle, if the purpose of requiring payment of compensation is to require the defendant to bear the cost of the harm eventuating from his or her negligent conduct, it is far from clear why that burden should be imposed in circumstances where the harm could only have arisen from breach of another element of the duty. Once the trial judge was not persuaded that a warning as to bilateral femoral neurapraxia would have led to a postponement of the operation, why should the practitioner bear responsibility for breach of a separate duty to warn of a risk which did not materialise? Recovery in such circumstances appears opportunistic.

174 If recovery of compensation were to be accepted in this case, it would be on the basis of the negligent failure to warn of the catastrophic risk, while the injury suffered was the bilateral femoral neurapraxia. The causal relationship would be established by a finding (yet to be made) that, if warned of the potentially catastrophic risk, the appellant would not have undergone the procedure. On that analysis, any harm which resulted from the operation would have been sufficient to attract compensation. Whether the harm which in fact resulted was a risk as to which a warning should have been given would appear not to be a relevant consideration, once it is found that, if a warning as to that risk had been given, the appellant would nevertheless have proceeded with the operation. The same result would follow if the warning had in fact been given and, consistently with the finding of the trial judge, the appellant had proceeded to undergo the operation. However, it is hard to identify a principled basis upon which a practitioner should be made legally responsible to pay compensation to a person who suffered an adverse outcome as to which he or she had been properly advised and had accepted. By contrast, there is a clear justification for imposing liability on a medical practitioner in respect of the harm suffered where an adverse outcome of which a warning should reasonably have been given, but was not, has come to pass. The principle which supports recovery in the latter case cannot, without some significant variation or expansion, justify recovery in the present case.

175 Section 5D does not clearly compel one answer to this question, rather than another. The language of the section involves (inevitably) a level of generality, which does not easily cover the circumstance where the negligence is a failure to warn of risks which inhere in a procedure carried out with due care and skill. Although it may be said that a number of physical conditions were "necessary" for the occurrence of the harm in the present case, the failure to warn of the risk which came to pass was not one. Accordingly, that aspect of the negligence of the respondent did not bear that causal relationship with the outcome sufficient to warrant imposing on him responsibility for that harm. That conclusion is at least consistent with the language of s 5D(1)(a). Alternatively, if the exclusion of something which otherwise qualifies as a necessary condition of the injury depends on a normative judgment, then it is appropriately excluded in the present case, pursuant to s 5D(1)(b) and (4).

176 The general law authority (limited as it is) weighs in favour of the conclusion reached by the trial judge, namely that relevant negligence had not been established.

177 If the weight of general law authority, to be applied pursuant to the statutory scheme, were not against a finding of liability in the present case, it would be necessary to consider whether legal principle warranted an extension of existing authority to cover the case. There are significant reasons for this Court declining such an expansion of the area of liability.

178 As explained by Kirby J in Rosenberg at [143], there is an extensive literature suggesting that the law in respect of this aspect of the patient-practitioner relationship has tended to part company with reality, in the sense that the assumptions upon which the "duty to warn" is based are fictitious or at least exaggerated. There is empirical evidence that many patients do not want and do not know how to cope with the uncertainty created by such warnings. Further, many patients go to a practitioner for skilled advice, not to be given a smorgasbord of considerations they are ill-equipped to assess. (These and related issues are exposed and analysed with clarity by Gerd Gigerenzer in Reckoning with Risk (Penguin, 2002) at pp 100-101.) The law rarely asks whether a warning should be given in a particular form and how it would be understood by the patient. For example, if a practitioner advising a particular procedure says, "the medical literature reveals that this procedure is associated with adverse consequence 'x' at the rate of 1%, but I have done the procedure 1,000 times, with no case of adverse consequences", the patient might infer that this practitioner is particularly expert, or that she is facing a string of adverse outcomes in the near future. Without attention to the precise form, content and context in relation to particular risks, the imposition of legal liability will not further the purposes underpinning the law.

179 In Rosenberg, Kirby J supported the obligation mandated by Rogers on a number of bases at [145]. Whether those considerations would favour an expansion of the current limit of liability is not a matter which can properly be resolved by this Court, but should properly be addressed by the High Court, or the Parliament.

180 The trial judge undertook a careful analysis of the evidence and the law and dismissed as irrelevant the possible failure to warn of the risk of a catastrophic outcome (as to which there was conflicting evidence). He was correct to do so. The appeal should be dismissed with costs.

181 Since writing the above, I have had the opportunity to read the reasons of the President. To the extent to which our reasoning is consistent, I agree with his more expansive analysis of the issues. To the extent we differ, primarily as to whether s 5D demands a rigid separation of physical and policy considerations in assessing causation, I would accept his alternative analysis, if thought to be preferable. It does not affect the result in the present case.

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Decision last updated: 13 April 2012