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Causation in failure to warn cases: High Court finds in favour of neurosurgeon

NewsFlash 24 May 2013

Wallace v Kam [2013] HCA 19 (8 May 2013)

The May 2013 High Court decision of Wallace v Kam [1] provides important guidance on liability and causation in failure to warn cases. The High Court unanimously held that a patient was not entitled to be compensated for a physical injury when he was prepared to accept the risk of it occurring.


TressCox Lawyers represented Dr Andrew Kam, a neurosurgeon who operated on Mr Ian Wallace’s lumbar spine in November 2004. This procedure had several inherent risks. The first risk was temporary damage to the nerves in Mr Wallace’s thighs, known as bilateral femoral neurapraxia. The second risk was a 1 in 20 chance of paralysis due to spinal nerve damage. Importantly, these risks were distinct and not related to each other. The surgery was unsuccessful and Mr Wallace developed neurapraxia, which caused him significant pain for some time. Mr Wallace did not suffer paralysis as a result of the surgery.

Dr Kam gave evidence in the original Supreme Court trial that he warned Mr Wallace about the risk of paralysis and nerve damage. However, the trial judge did not make a finding on this point. The NSW Court of Appeal and the High Court proceeded on a hypothetical finding that Dr Kam failed to warn Mr Wallace about the risk of paralysis.

In the original Supreme Court trial, Mr Wallace argued that he would not have had surgery had he been warned about either risk. After this submission was rejected, Mr Wallace argued in the NSW Court of Appeal that he would not have gone ahead with surgery had he been warned about the risk of paralysis. This means that he would have decided to have surgery if warned about neurapraxia, but not paralysis. This causation argument was unanimously rejected by the High Court.

Causation in Failure to Warn Cases

The High Court provided a useful explanation of the difference between duty of care and causation. Duty of care is a ‘forward-looking rule’, focussing on what is reasonably foreseeable. Causation is a ‘backward-looking rule’, concerned with who or what was responsible for an injury. Given the different focus of these two concepts, it is possible for a person to breach their duty of care, but not be the cause of a reasonably foreseeable injury.

The High Court explained that two questions must be answered to determine causation in a failure to warn case:

  1. how did the injury occur?
  2. should legal responsibility for that injury be attributed to the doctor?

This is consistent with the statutory requirements in section 5D(1) of the Civil Liability Act 2002 (NSW) (the Act). In addition, section 5D(3) of the Act explains that causation must be determined subjectively in light of all the relevant circumstances, and any statement made by the plaintiff after suffering harm about what he or she would have done is inadmissible.  This means that the onus was on Mr Wallace to prove that he would not have had surgery had he been warned of the risk of neurapraxia or paralysis. It was not available to Mr Wallace to simply say that he would not have had surgery had he been warned about all material risks.

The High Court found that the duty to warn patients of material risks is imposed by reference to the common law right of a patient to choose whether or not to undergo a proposed medical treatment. However, this common law right does not operate to protect the patient’s right to choose or to protect from exposure to all unacceptable risks. The underlying policy of the duty to warn is to protect the patient from a physical injury that represents an unacceptable risk to that patient. This means that a doctor cannot be found liable for a physical injury that occurs when a patient was warned about and prepared to accept that risk of medical treatment or surgery.

Unanimous Finding

In upholding the decision of the NSW Court of Appeal, the High Court found that Mr Wallace’s position was no different than had he decided to proceed with surgery after Dr Kam had properly warned him about the risk of suffering neurapraxia. This is because Mr Wallace would have opted to have surgery even if he knew about the risk of neurapraxia. This means that any potential failure to warn was not causative of Mr Wallace’s injury and liability for him suffering neurapraxia should not be attributed to Dr Kam. Accordingly, Mr Wallace was not entitled to be compensated for a physical injury when he was prepared to accept the risk of it occurring.

The High Court explained that its decision is consistent with the law in America. The position in the United States is that a ‘patient obviously has no complaint’ if he or she would have consented to treatment after being told of the risks [2]. Therefore, ‘[a]bsent occurrence of the undisclosed risk, the doctor’s omission is legally inconsequential’ [3].


The decision of Wallace v Kam demonstrates that simply proving a doctor has breached his or her duty or care is not enough to be successful in a failure to warn case. Duty of care and causation are distinct concepts that must be analysed separately. Whilst warning patients about material risks is a vital responsibility of all doctors, a failure in this area is not always a fatal blow for medical defence organisations and their clients.

[1] [2013] HCA 19 (8 May 2013).
[2] Canterbury v Spence 464 F 2d 772 at 790 (1972).
[3] Downer v Veilleux 322 A 2d 82 at 92 (1974).

John Petts, Partner

Cindy Tucker, Partner

NewsFlash 24 May 2013
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