Following the publication of the Ipp Report on 30 September 2002, most states and territories in Australia implemented statutory provisions to supplement common law negligence principles in relation to causation and remoteness of damages. The new legislative regime introduced a two-pronged approach to causation by reference to the notions of “factual causation” and “scope of liability”; giving weight to whether the negligent conduct actually played a role in bringing about the relevant harm, as well as whether policy considerations would support the extension of the defendant’s liability to that harm.
The High Court of Australia has considered the notion of “factual causation” on a number of occasions since the introduction of the Ipp legislative reforms. While it appears settled that factual causation is determined by reference to the “but for” test, the “scope of liability” is becoming an issue Australian courts are grappling with more and more often. In May this year, the High Court handed down its decision in Wallace v Kam, a medical negligence case involving a failure to warn. In the course of its judgment, the High Court considered the concepts of factual causation and scope of liability in depth, and particularly the latter. The High Court’s judgment provides useful guidance on how to navigate both these ideas, extending from medical negligence to product liability and beyond, both here and overseas.
As we know, following proof of duty and breach, the tort of negligence requires that the breach first caused the relevant injury or loss, and that injury or loss was not too remote a consequence of the breach. Civil liability legislation in most states and territories now provides the following supplementary rules (the provisions below are contained in section 5D of the Civil Liability Act 2002 (NSW), but are mirrored in each relevant state and territory):
(1) A determination that negligence caused particular harm comprises the following elements:
(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:
(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.
According to the Ipp Report:
In Wallace v Kam, Mr Wallace underwent a surgical procedure performed by Dr Kam to alleviate pain in his lower spine caused by a disc protrusion. There were two distinct inherent risks involved in the procedure that Mr Wallace was not advised of:
The first risk materialised, and Mr Wallace sustained neurapraxia which left him in severe pain for some time. The risk of paralysis did not materialise.
Accordingly, the central issue was that of causation; if Dr Kam had not negligently failed to warn Mr Wallace of the two risks, would Mr Wallace have suffered the injury he did?
At trial, the Supreme Court of New South Wales found that Dr Kam had been negligent in failing to inform Mr Wallace of the risk of neurapraxia. However, the Supreme Court also found that Mr Wallace would have elected to go ahead with the surgery even if he had been made aware of that risk. Accordingly, the surgeon’s negligent failure to warn did not cause the patient’s harm. The Court declined to make any finding about whether Dr Kam had negligently failed to warn Mr Wallace of the risk of paralysis on the basis that risk never manifested. On appeal, the Court of Appeal split 2:1, but the majority also considered it was not appropriate to hold the surgeon liable for the patient’s neurapraxia on the basis of negligence relating to a separate risk, being paralysis, which did not materialise.
The High Court upheld the decisions of both courts below. There was no question Dr Kam owed Mr Wallace a duty to exercise reasonable care and skill, and further, no question he breached that duty by failing to warn Mr Wallace of two material risks of injury. In relation to factual causation, the High Court emphasised that “the determination of factual causation in accordance with s 5D(1)(a) involves nothing more or less than the application of a “but for” test of causation.” Taking that approach, the High Court held that factual causation was made out because Mr Wallace would not have chosen to undergo the procedure at all if warned of all material risks, and therefore, not have sustained the neurapraxia.
In relation to the scope of liability, the High Court explained:
[s]ection 5D guides but does not displace common law methodology.
A limiting principle of the common law is that the scope of liability in negligence does not extend beyond liability for the occurrence of such harm the risk of which it was the duty of the negligent party to exercise reasonable care and skill to avoid.
Within that limiting principle of the common law, the scope of liability for the consequences of negligence is often coextensive with the content of the duty of the negligent party that has been breached … However, the scope of liability in negligence is not always so coextensive … That is in part because the elements of duty and causation of damage in the wrong of negligence serve different functions (the former imposing forward-looking rule of conduct; the latter imposing a backward-looking attribution of responsibility for breach of the rule) with the result that the policy considerations informing each may be different.
Applying this framework, the High Court held that it was not appropriate for the scope of Dr Kam’s liability to extend to the physical injury sustained by Mr Wallace. It came to this conclusion by applying a hypothetical test to determine whether, hypothetically, if Dr Kam had warned Mr Wallace of the risk of neuropraxia, he would have undergone the procedure anyway. Applying the principle developed in Rosenberg v Percival, the High Court considered Mr Wallace’s position subjectively, on the evidence given, and confirmed that Mr Wallace’s own evidence as to what he would have done was inadmissible unless it was against his own interest.
Accordingly, the High Court found that although Mr Wallace would not have chosen to undergo the surgical procedure had he been properly warned of all material risks (neurapraxia and paralysis), he would have chosen to undergo the surgical procedure had he been warned only of the risk that actually materialised (neurapraxia). On that basis, Mr Wallace should not be compensated for the materialisation of a risk he would have been prepared to accept.
The High Court clarified that the conception of a duty to warn was not intended to protect of a person's right to choose, or to protect a person from exposure to all unacceptable risks. Rather, the policy is to protect a person from a particular injury or injuries, the risk of which is unacceptable to them.
Although Wallace v Kam dealt with a medical practitioner, the decision necessarily has implications for product liability failure to warn cases. Just as medical practitioners have a duty to their patients to warn of all “material risks” of injury inherent in any treatment they propose, a manufacturer has a similar duty to warn consumers of any known risks of using a product. As above, Wallace v Kam clarifies that the scope of liability in failure to warn cases is limited to whether the defendant failed to warn of a particular risk that in fact eventuated, and does not extend to a failure to warn of different risks that the plaintiff either accepted, or would have accepted.
In a product liability sense, this is significant. For example, a certain drug may have a number of side effects, but its manufacturer only warns of a handful. A consumer could purchase that product, and suffer an undisclosed side effect. However, if the evidence shows that consumer, on a subjective and hypothetical approach, would have purchased the drug even if he or she knew of that side effect, a court applying the High Court’s reasoning in Wallace v Kam cannot extend the manufacturer’s scope of liability to loss or damage suffered as a result of that side effect.
This said, it is worth noting that in Wallace v Kam, the High Court did identify the fact that a number of failings to warn would have a cumulative effect which may result in a finding of liability. This is ultimately something that would need to be considered on a case by case basis. In any event, the normative requirements posited by the “scope of liability” limb act as an impediment to any prospective plaintiff where the civil liability legislation applies.
The decision also has potential international ramifications. While a number of international jurisdictions have adopted similar distinctions at common law between issues of factual causation and “legal” causation, the High Court has taken this one step further. For example, the most current Restatement of the law of torts in the United States introduced the separate notions of “factual causation” and the “scope of liability” for the first time. Previously, causation was dealt with under the heading of “legal causation,” which covered both facts and scope, and was often further confused with the term “proximate causation,” which alternatively refers to scope and facts, or scope individually. The Supreme Court of Canada has also drawn a distinction between factual causation and scope of liability. Indeed, in Wallace v Kam, the High Court made reference to this international jurisprudence, and the fact that its decision was coming into line with the position overseas. While the High Court used the term “proximate causation,” it made clear it was referring to United States case law that specifies that causation can only be proved if an undisclosed risk manifests into an actual injury, and that absent the occurrence of the undisclosed risk, a practitioner or manufacturer’s omission is “legally inconsequential”.
The High Court has now gone beyond this, adding the further condition that the undisclosed risk must be one a plaintiff is unwilling to hazard. The effect of this on individual claims is that plaintiffs have a higher hurdle to overcome. The effect on product liability class actions arising is more interesting, because it highlights the subjective, individual element a court must consider in a failure to warn case. Many Canadian and United States courts are already reluctant to allow failure to warn actions to gain class certification and proceed as a class action, given the unique issues of causation usually raised by individual class members. Even in Australia, where formal certification is not necessary, attacking the lack of sufficient commonality between members in a group could prove fruitful for defendants faced with failure to warn class actions, on the basis that such cases require a thorough examination of the individual plaintiff’s situation in constructing the hypothetical enquiry of whether, if the defendant had given an adequate warning of the product or procedure’s risk, the plaintiff would have proceeded in undergoing the procedure.
For these reasons, the international and domestic implications of the judgment will be particularly interesting to monitor. Watch this space.
Click 'Download' to view the original article, which appeared in the Australian Product Liability Reporter.
 Civil Law (Wrongs) Act 2002 (ACT), Ch 4 Pt 4.3; Civil Liability Act 2002 (NSW), Pt 1A Div 3; Civil Liability Act 2003 (Qld); Civil Liability Act 1936 (SA) Pt 6 Div 2; Civil Liability Act 2002 (Tas), Pt 6 Div 3; Wrongs Act 1958 (Vic) Pt X Div 3; Civil Liability Act 2002 (WA) Pt 1A Div 3
 See, for example, the Supreme Court of Canada decision of Mustapha v. Culligan of Canada Ltd. 2 SCR 114 and the concept of a “proximate cause” in medical failure to warn cases in the United States, for example Cochran v Wyeth Inc 3 A 3d 673 (2010).
 Restatement of the Law, Third, Torts: Liability for Physical and Emotional Harm (American Law Insitute, 2011). In United States jurisprudence, Restatements of the Law are treatises that inform judges and lawyers in relation to various principles of common law.
 See for example, the recent refusal of the Quebec Superior Court certify a class action brought against drug manufacturer Hoffmann-La Roche Limited over a ‘failure to warn’ of the side-effects of using the anti-infallmatory drug Accutane.
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