Duty to Warn and Causation: Wallace v Kam

By Professor Loane Skene

Wallace v Kam Case Page

The recent case of Wallace v Kam [2013] HCA 19, a unanimous judgment of the High Court of Australia, continues a trend of a rigorous application of the principles of causation in duty to warn cases within the context of medical negligence. While emphasising that patients have a legal right to make their own medical decisions, and that doctors have a legal duty to inform patients about material risks of a proposed treatment (as stated in Rogers v Whitaker [1992] HCA 58) the judgment calls for more careful scrutiny of whether doctors should be held responsible for the patient’s injury or loss in certain duty to warn cases.

The judgment also answers a vital question about causation. If a doctor negligently does not inform a patient about two or more material risks of a treatment, is the patient entitled to compensation if he or she would have agreed to take the risk that materialised, but not a risk that should have been mentioned but did not materialise? The court held that the doctor would not be liable. The patient’s claim could only succeed if the doctor negligently failed to mention a risk that the patient would not have been prepared to accept; and that risk materialised. The patient could not succeed only by satisfying the court that the patient would not have agreed to the treatment if properly informed of the other risk; that is, but for the doctor’s negligence in not disclosing the other risk, the patient would not have had the treatment and suffered the injury. Proof of that matter might establish factual causation but not that the doctor should be held responsible (‘scope of liability’).

The history of the duty to inform patients about material risks of treatment

It is more than 20 years since the High Court of Australia stated in Rogers v Whitaker that a doctor’s duty of care for a patient includes a duty to inform the patient about ‘material’ risks of a proposed treatment, so that patients can decide for themselves whether they are prepared to accept those risks by agreeing to undertake the treatment. Since then, there has been a stream of cases alleging that doctors have negligently failed to disclose a material risk, causing the patient an injury or loss that would not have occurred if the patient had been properly informed and refused the treatment. Initially, many patients were successful in those claims, especially in cosmetic surgery cases where the argument focussed on whether the risk in question was material in the circumstances and so should have been disclosed.

Later, however, the pendulum began to swing against patients in failure to warn cases on the ground of causation. Even if the patient had been warned of the material risk, would the patient still have agreed to the treatment, and so not sustained the injury or loss for which compensation is claimed? In Rosenberg v Percival [2001] HCA 18 the plaintiff failed because she was not able to prove causation. Her assertion that she would not have agreed to undergo an osteotomy if warned of the risk of temperomandibular joint disorder was not accepted on the facts of the case. The Australian test of causation is subjective (what would this patient have done?); but such statements by patients after the event are inevitably self-serving and must be examined in the light of other evidence. To take account of what Chief Justice Gleeson in Rosenberg v Percival called the ‘prism of hindsight’, as Justice Hoeben noted in Richards v Rahilly [2005] NSWSC 352, ‘[t]he reliability of such evidence needs to be assessed by reference to other evidence’.

The Australian civil liability legislation mentioned later in this post also tightened the principles of causation. The legislation requires proof of more than ‘factual causation’ to establish liability (that the defendant’s negligence, as a matter of fact, caused the patient’s injury or loss). It also requires that the defendant should be held responsible in those circumstances (that is, that the defendant was within the appropriate ‘scope of liability’ that should be imposed). In some jurisdictions, the legislation prohibits patients testifying about what they would have done if warned of the risk in question, unless that evidence would be against their interests, as in s 5D(3)(b) of the Civil Liability Act 2002 (NSW).

Wallace v Kam represents another indication of how the courts and the legislature have tightened causation in medical negligence cases.

The facts of and history of Wallace v Kam

Mr Wallace suffered from a condition of the lumbar spine and Dr Kam, a neurosurgeon, performed a surgical procedure on him. There were various risks of this procedure but the argument focussed on two of them. One was a relatively minor risk — the patient could suffer ‘temporary local damage to nerves within his thighs … resulting from lying face down on the operating table for an extended period’ (described as ‘bilateral femoral neurapraxia’) (at [1]). The second risk was more serious. There was a ‘one-in-twenty chance of permanent and catastrophic paralysis resulting from damage to his spinal nerves’ (at [1]). Dr Kam did not mention either of these risks to the patient before undertaking the surgery. It was not successful. The patient’s lumbar spine condition did not improve and he sustained neurapraxia causing severe pain for some time. However, he did not develop paralysis, the more serious of the two risks.

Mr Wallace sued Dr Kam, alleging that he had negligently failed to warn him about the two risks of the surgery and that the failure to disclose had caused the patient’s injury, because if he had been warned about either of the risks, he would not have agreed to the surgery and so would not have suffered the injury. Thus, there were two issues. The first was breach (was Dr Kam in breach of his duty of care to the patient by not warning him of a material risk?). The second was causation (if the patient had been warned about the risk/s, would he still have agreed to the surgery?). The law on the former is based on common law principles and is relatively clear. The law on causation is more complex, being based partly on common law and partly on the civil liability legislation that implemented ‘tort law reform’, in this case, the Civil Liability Act 2002 (NSW).

Mr Wallace’s claim was dismissed at trial. Justice Harrison found that Dr Kam was negligent in not warning Mr Wallace of the risk of neurapraxia, but even if he had been warned of that risk, the patient would have chosen to have the procedure. As summarised by the High Court, Justice Harrison held that ‘[t]he “legal cause” of the neurapraxia [in the plaintiff] “could never be the failure to warn of some other risk that did not materialise”’. Mr Wallace appealed to the Court of Appeal of the Supreme Court of New South Wales, which was divided on the causation issue (the ‘scope of liability’ aspect discussed below). President Allsop and Justice Basten agreed with the trial judge; Justice Beazley did not and would have ordered a new trial. Mr Wallace appealed to the High Court, on the ground that the Court of Appeal had erred in holding that the legal cause of the neurapraxia could not be the failure to warn of the risk of paralysis. The High Court also rejected his claim (Chief Justice French, Justices Crennan, Kiefel, Gageler, and Keane).

Why was there no liability for the failure to warn of the risk which transpired?

The High Court cited the principles in Rogers v Whitaker concerning a doctor’s duty to ‘exercise reasonable care and skill’ in treating a patient, which includes warning the patient about the ‘material risks’ of physical injury in a proposed treatment before the patient agrees to it. As the High Court said in Wallace, this duty to warn ‘is founded on the underlying common law right of the patient to choose whether or not to undergo a proposed treatment’ (at [8]). In other words, it is up to the patient to choose which risks he or she is willing to take; and the patient is entitled to be compensated for the loss of the opportunity to make that choice.

However, a doctor who is found to have breached his or her duty to warn a patient of a material risk is only liable if that breach caused the patient’s injury or loss. This common law principle is now stated in s 5D of the Civil Liability Act 2002 (NSW) (and similar civil liability legislation in all states and the Australian Capital Territory). Section 5D refers to two aspects of causation. The first is ‘factual causation’ (that the defendant’s negligence was ‘a necessary condition of the occurrence of the harm’. This is a matter of fact and it is determined by the ‘but for’ test of causation — ‘that the harm that in fact occurred would not have occurred absent the negligence’ (at [14], [16]). In a case where a doctor has negligently failed to warn a patient about material risks of a proposed treatment, this aspect of causation could be established if the patient can prove on a balance of probabilities that he or she would not have agreed to the procedure if warned of other risks, and so would not have sustained the injury, as in Wallace v Kam (at [29]). What the patient would have done if warned is determined subjectively (s 5D(3)(a)) but, under s 5D(3)(b), the patient’s own evidence of what he or she would have done is inadmissible except to the extent that it is against the patient’s interests.

The second aspect of causation is the ‘scope of liability’ (‘that it is appropriate for the scope of the negligent person’s liability to extend to the harm so caused’: s 5D(1)). This is ‘normative’ ‘whether or not, and if so why, responsibility for the harm should be imposed on the negligent party’ (at [14]), which is ‘properly answered by a court by the application of precedent’ (at [22]) and requires more articulation of policy than ‘directness’, ‘reality’, effectiveness’, ‘proximity’ or ‘common sense’ (at [23]).

In the Court of Appeal, Justice Beazley (dissenting) believed it was appropriate for Dr Kam to bear the responsibility of compensating Mr Wallace because he had breached his duty to warn him of the risk of neurapraxia and that risk materialised. As the High Court paraphrased his reasoning, the scope of the liability was aligned with the scope of the duty (at [31]). However, the majority judges in the Court of Appeal, as paraphrased by the High Court, said that ‘Mr Wallace should not be compensated for the materialisation of a risk he would have been prepared to accept’ (at [32]). As the High Court said, ‘[t]he underlying policy [of the law on duty to warn] is … to protect the patient from the occurrence of physical injury the risk of which is unacceptable to the patient’ (at [36]). There might be an exception where the risks are not separate and distinct as in this case, but accumulated together (at [34] and [36]; this point was not explored in the judgment).


Doctors have often expressed concern about their legal duty to mention ‘every risk’ of a proposed treatment and their potential liability if they fail to mention a particular risk, even if it seems remote. The judgment in Wallace v Kam should reassure them and their liability insurers that even if doctors do not mention a risk that should perhaps be mentioned, they will not be held liable unless that risk materialises and there is evidence to persuade the court that the patient would not have agreed to the treatment if warned of that particular risk.

Patients may be concerned that they will have no remedy if a doctor does not warn them about risks that would have been material for them but did not materialise. To that extent, the doctor’s duty to inform may appear to be undermined. However, that is always the case in negligence actions. However culpable a defendant’s conduct may have seemed, the plaintiff has no remedy unless he or she suffered injury or loss that was caused by the defendant’s breach of duty towards the plaintiff.

AGLC3 Citation: Loane Skene, ‘Duty to Warn and Causation: Wallace v Kam’ on Opinions on High (5 July 2013) <http://blogs.unimelb.edu.au/opinions-on-high/skene-wallace/>.

Professor Loane Skene is Professor of Law and Director of Studies, Health and Medical Law at Melbourne Law School and Adjunct Professor, Faculty of Medicine, Dentistry and Health Sciences at The University of Melbourne.

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About Loane Skene

Loane Skene has been a Professor at Melbourne Law School and Adjunct Professor in the Medical Faculty for 13 years. Earlier, she was a solicitor in Melbourne and the United Kingdom and a policy adviser in Canada and Melbourne (spending ten years with the Victorian Law Reform Commission). She is author of the widely used textbook Law and Medical Practice: Rights, Duties, Claims and Defences and has written numerous book chapters and articles in Australian and international legal, medical and scientific journals. Her current research interest is ownership of bodily material, a project undertaken with colleagues at the Oxford Law School.