In other words, material increase in risk does not involve a necessary finding of causation.
62 Where there are competing alternative causes, or where the aetiology of a disease is uncertain, a "robust approach" to drawing inferences or even a reversal of the onus of proof may have particular justifications. A failure to discharge a duty of disclosure involves somewhat different considerations. It was a breach of that duty which was addressed in Chappel v Hart (1998) 195 CLR 232, a year after the discussion in Bendix.
63 Mrs Hart required throat surgery to remove a pharyngeal pouch. The condition was not merely unpleasant, but progressive. It required surgery and Mrs Hart did not suggest that a warning of the attendant risks would have led her to avoid surgery altogether. Rather, the inference to be drawn from the evidence was that the risk would diminish with the skill and experience of the surgeon and Mrs Hart asserted that, had she been aware of the risk, she would have obtained the services of the best surgeon available. The risk in question was one of infection following perforation of the oesophagus, with consequent loss of her vocal capacity. The question which vexed the Court was whether the failure to warn had a relevant causal connection with the materialisation of the risk. The Court divided in relation to the relevant inference available on the facts. Thus, the majority, comprising Gaudron, Gummow and Kirby JJ in separate judgments relied on evidence that with a more experienced surgeon there would have been a lower risk of the harm. The dissenting judges, McHugh and Hayne JJ, took a different view of the evidence, McHugh J stating at [41]:
"It is also true that the risk of perforation will vary depending upon the degree of care taken on a particular occasion. But the evidence did not suggest, let alone prove, that an operation by the defendant carried with it a statistically significant greater risk of perforation than that of any other qualified surgeon. … The evidence was all one way that perforation of the oesophagus was an inherent risk of the procedure."
64 To similar effect Hayne J held at [133]:
"There was evidence that if she had been properly advised of the risks to her voice, the respondent would not have had the procedure performed by the appellant, but by another doctor. There was, as I have said, some evidence which suggested that the better the doctor, the less the chance of perforation of the oesophagus. That evidence was, at best, exiguous and stopped far short of identifying any sound basis for assessing what effect the surgeon's skills may have had on the unusual chain of events which happened in this case."
65 Those points of departure being noted, it is apparent that all members of the Court (with the exception of Hayne J) appear to have adopted an approach which accepted that a temporal connection between the breach of duty and the harm suffered, being a materialisation of the risk involved in the failure to warn, in the absence of a persuasive contrary explanation, could suffice to establish a relevant causal connection. Thus, at [8], Gaudron J stated:
"The duty was not performed and the risk eventuated. Subject to a further question in the case of a duty to provide information, that is often the beginning and end of the inquiry where the breach of duty materially caused or contributed to the harm suffered. As Dixon J pointed in Betts v Whittingslowe (1945) 71 CLR 637 at 649, albeit in relation to a statutory duty, 'breach of duty coupled with an accident of the kind that might thereby be caused is enough to justify an inference, in the absence of any sufficient reason to the contrary, that in fact the accident did occur owing to the act or omission amounting to the breach.'"
66 The second sentence in this passage, taken in isolation, is unclear: on one view it treats causation as an assumed element, but that may need to be understood in the context of what follows. The "further question" to which her Honour alluded appears to be that set out and answered in the following paragraph [9]:
"Where there is a duty to inform it is, of course, necessary for a plaintiff to give evidence as to what would or would not have happened if the information in question had been provided. If that evidence is to the effect that the injured person would have acted to avoid or minimise the risk of injury, it is to apply sophistry rather than common sense to say that, although the risk of physical injury which came about called the duty of care into existence, breach of that duty did not cause or contribute to that injury, but simply resulted in the loss of an opportunity to pursue a different course of action."
67 This latter requirement will, no doubt, be read subject to the caution often given in relation to the weight to be placed upon the evidence, inevitably given with the benefit of hindsight, as to what the patient would have done in the hypothetical event. Although the issue does not arise in this case, it may be noted that, in cases to which the Civil Liability Act 2002 (NSW) applies (this not being such a case) the Court will be deprived of such indisputably relevant evidence by operation of s 5D(3)(b).
68 McHugh J, although in the minority, adopted a similar approach. Thus, at [27], his Honour held:
"Before the defendant will be held responsible for the plaintiff's injury, the plaintiff must prove that the defendant's conduct materially contributed to the plaintiff suffering that injury. In the absence of a statute or undertaking to the contrary, therefore, it would seem logical to hold a person causally liable for a wrongful act or omission only when it increases the risk of injury to another person. If a wrongful act or omission results in an increased risk of injury to the plaintiff and that risk eventuates, the defendant's conduct has materially contributed to the injury that the plaintiff suffers whether or not other factors also contributed to the injury occurring."
69 Further, his Honour stated at [34]:
"The foregoing observations lead me to the following conclusions concerning whether a causal connection exists between a defendant's failure to warn of a risk of injury and the subsequent suffering of injury by the plaintiff as a result of the risk eventuating: (1) a causal connection will exist between the failure and the injury if it is probable that the plaintiff would have acted on the warning and desisted from pursuing the type of activity or course of conduct involved; … (6) the onus of proving that the failure to warn was causally connected with the plaintiff's harm lies on the plaintiff. However, once the plaintiff proves that the defendant breached a duty to warn of a risk and that the risk eventuated and caused harm to the plaintiff, the plaintiff has made out a prima facie case of casual connection. An evidentiary onus then rests on the defendant to point to other evidence suggesting that no causal connection exists. Examples of such evidence are: evidence which indicates that the plaintiff would not have acted on the warning because of lack of choice or personal inclination; evidence that no alternative course of action would have eliminated or reduced the risk of injury. Once the defendant points to such evidence, the onus lies on the plaintiff to prove that in all the circumstances a causal connection existed between the failure to warn and the injury suffered by the plaintiff."
70 In Chappel at [68] and [69] Gummow J stated:
"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.
In those circumstances the task of Dr Chappel was to demonstrate some good reason for denying to Mrs Hart recovery in respect of injuries which she would not have sustained at his hands but for his failure adequately to advise her."
71 Kirby J set out a number of principles relating to evaluation of causation, not limited to cases of failure to disclose information: at [93]. At sub-par 8 (p 273), his Honour noted the shifting evidentiary onus in the following terms:
"Once a plaintiff demonstrates that a breach of duty has occurred which is closely followed by damage, a prima facie causal connection will have been established. It is then for the defendant to show, by evidence and argument, that the patient should not recover damages."
72 Since the decision in Chappel v Hart, in Naxakis v Western General Hospital (1999) 197 CLR 269, Gaudron J, at [31] cited with approval the statement of principle set out above from McHugh J in Chappel at [27]. Kirby J repeated at [76] the principle he had enunciated in Chappel, as set out above, and Callinan J also adopted the statement of principle enunciated by McHugh J in Chappel at [27]. In Rosenberg v Percival (2001) 205 CLR 434 at [88] Gummow J adopted the remarks of McHugh J in Chappel at [34].
73 Despite commentary to the effect that there has been a failure to clarify the correct approach to these questions - see Gunson, "Turbulent Causal Waters: The High Court, Causation and Medical Negligence" (2001) 9 Tort LR 53 - the principles stated by four members of the Court in Chappel v Hart and in particular as explained by McHugh J, now adopted by a majority of the Court, without express dissent, should be treated as the correct statement of the law. That approach was followed by the Full Court of the Supreme Court of South Australia in Zaltron v Raptis [2001] SASC 209 at [90] (Martin J, Doyle CJ and Williams J agreeing; a fact noted again without adverse comment by Gaudron and Kirby JJ in rejecting special leave to appeal: see transcript of proceedings, 19 April 2002, Zaltron v Raptis.
74 Since Chappel v Hart, the High Court has revisited causation in a number of different contexts: see, for example, Kirby J in Great China Metal Industries Co Ltd v Malaysian International Shipping Corporation, Berhad (1999) 196 CLR 161 at [146] (considering the operation of the Hague Rules in relation to carriage of goods by sea); Chen Shi Hai v Minister for Immigration and Multicultural Affairs (2000) 201 CLR 293 at [24]-[37] (Gleeson CJ, Gaudron, Gummow and Hayne JJ) and [66]-[74] (Kirby J) (considering "for reasons of" in the Refugees Convention); Kenny & Good Pty Ltd v MGICA (1992) Ltd (1999) 199 CLR 413 at [25]-[28] and [26] (Gaudron J) and [107] and [108] (Kirby and Callinan JJ) (liability of valuer for negligent valuation); Henville v Walker (2001) 206 CLR 459 and I & L Securities Pty Ltd v HTW Valuers (Brisbane) Pty Ltd (2002) 210 CLR 109 at [56] and Travel Compensation Fund v Tambree T/as Tambree and Associates (2005) 80 ALJR 183 at [28]-[32] (Gleeson CJ); [45]-[48] (Gummow and Hayne JJ); [71]-[73] (Kirby J) and [79]-[82] (Callinan J) (claims for damages under the Trade Practices Act); McCann v Switzerland Insurance Australia Ltd (2000) 203 CLR 579 at [47]-[53] (Gaudron J), [73] and [74] (Kirby J), [130] (Hayne J), [190]-[197] (Callinan J) and Purvis v New South Wales (2003) 217 CLR 92 at [161]-[166] (McHugh and Kirby JJ), [231]-[236] (Gummow, Hayne and Heydon JJ) (disability discrimination). From these examples, three broad propositions can be derived. First, where there are multiple 'effective' causes of an event, of which only one involves a breach of duty, causation may nevertheless be established, so long as the breach of duty makes a "material contribution" to the harm suffered. Secondly, the fact that the breach of duty is a cause in the sense noted, may not be sufficient to establish liability; the degree of connection must satisfy the policy underlying the legal attribution of responsibility. Thirdly, and consequentially, care must be taken to assess causation in its particular statutory or other legal context. Even within general law principles relating to tort, the underlying purpose of the particular assessment must be borne in mind.
75 Where it is demonstrated that a defendant has breached a duty owed to a plaintiff, and harm has followed, it would be understandable that the law might impose an onus on the defendant to show that his or her breach of duty had not caused the harm. However, that course has not been taken and it is clear beyond doubt that the burden of establishing causation lies on the plaintiff. On the other hand, in some circumstances the law has accepted that an inference of causation will arise from the existence of a temporal connection, together with other slender support. Thus where medical science is unable to confirm or deny a causal connection between exposure to a potentially harmful agent and a particular medical condition, courts have been willing to infer on the basis of "common sense" that a connection is established on the balance of probabilities. No such difficulty arose in Betts v Whittingslowe (1945) 71 CLR 637, relied on in Chappel v Hart, being a case involving an industrial accident, where the trial judge had not accepted the evidence of the plaintiff (a 14-year-old boy) as to how the accident occurred and hence there was no direct evidence on that point. Not all members of the High Court thought it necessary to decide how the accident occurred: see Starke J at 644. However, Dixon J did seek to identify the cause in order to determine whether it was caused by a breach of statutory duty. This merely required the identification of the most plausible of a number of hypotheses.
76 In other situations, an available inference involving causation may be more readily accepted where any inconsistent explanation would lie within the knowledge of the defendant, and is not proffered.
77 However, none of these situations is directly analogous of the present case, where causation depends upon a finding as to what the plaintiff would have done had he been given appropriate information. Further, where that assessment requires either a consideration of the subjective state of mind of the plaintiff, or the position which a reasonable person would take, if placed in the same position as the plaintiff, there is no obvious reason to call on the defendant to provide evidence that the plaintiff would have undergone the operation in any event. In fact, the nature of the evidentiary burden placed on the defendant is perhaps explained by the comment in Chappel v Hart (p 273) of Kirby J that it is for the defendant to show "by evidence and argument" that the patient should not recover damages. Further, there is some irony in the fact that the law is willing to assume a causal connection in such circumstances, absent proof to the contrary, but discounts the evidence of the plaintiff, which might provide the most direct support for such an assumption: see Ellis v Wallsend District Hospital (1989) 17 NSWLR 553 at 560E-F (Kirby P), 581F (Samuels J) (Meagher JA agreeing) and, generally, Rosenberg v Percival (2001) 205 CLR 434, albeit that the latter was a case in which the High Court upheld the finding of the trial judge rejecting the plaintiff's explanation as implausible.
78 It is clear, nevertheless, that two propositions flow from Chappel v Hart, relevantly for the present case. The first is that the element of causation must be established and, accordingly, absent agreement between the parties that this issue was not in dispute, the failure of the trial judge to make a finding in this respect demonstrated error. The second proposition is that evidence of a failure to provide information, particularly as to potential risks of the procedure, combined with the materialisation of those risks, is sufficient to establish a prima facie case of causation, which is capable of acceptance in the absence of a more plausible contrary inference.
79 These principles were accepted and applied in circumstances similar to those revealed by this case in Shead v Hooley [2000] NSWCA 362, at [53]-[56]. After reviewing the principles established in Chappel v Hart, Davies AJA (with whom Mason P and Beazley JA agreed) stated at [69]:
"Once it was shown that there was a failure on the part of Dr Shead to warn Ms Hooley of the risk of gastroparesis and that Dr Shead breached his duty of care towards his patient in failing to warn her of the risk, and once it was shown that the risk eventuated, then the law as enunciated in Chappel v Hart is that the breach of the duty should be treated as materially causing or contributing to the injury unless good reason to the contrary is shown. In the present case, no such reason was established. Dr Shead was unable to establish that the risk which Ms Hooley faced would not have been reduced if an adequate warning had been given. There was a possibility, even a probability, that, had a further opinion been obtained, a further gastroscopy would have been performed and the state of the chronic ulcer would or may have appeared different from that shown in the gastroscopies taken by Dr Elliott. It follows the causation was established."