(Wallace v Kam [2013] HCA 19)

Background

Mr Wallace sought medical assistance from Dr Kam, a neurosurgeon, for a condition relating to his lumbar spine. Dr Kam performed a surgical procedure on him which involved two main inherent risks. The first was of temporary local damage to a nerve within his thighs - described as "bilateral femoral neurapraxia," which could be brought about as a result of lying face down on the operating table for an extended period of time. The second was a 'one-in-twenty’ chance of permanent and catastrophic paralysis, resulting from damage to the spinal nerves.

The surgical procedure performed by Dr Kam was ultimately unsuccessful and the condition of Mr Wallace's lumbar spine did not improve. After the procedure, the first risk materialised in that Mr Wallace sustained neurapraxia which left him in severe pain.

Primary proceedings

Mr Wallace commenced proceedings in the Supreme Court of New South Wales seeking damages from Dr Kam in respect of the neurapraxia. He alleged that Dr Kam failed to warn him of the risks involved in the surgical procedure, including the risk of developing neurapraxia and the risk of paralysis. He claimed that, had he been warned those risks, he would have made the decision not to undergo the surgical procedure, and would therefore not have sustained the neurapraxia.

At first instance, Harrison J of the Supreme Court held that, although Dr Kam had negligently failed to warn Mr Wallace of the risk of neurapraxia, Mr Wallace would have chosen to undergo the surgical procedure even if warned of the risk. His Honour therefore concluded that Dr Kam's failure to warn Mr Wallace of the risk of developing neurapraxia was not a necessary condition of the occurrence of the neurapraxia. He declined to make a finding on whether Dr Kam negligently failed to warn Mr Wallace of the risk of paralysis and what Mr Wallace would have done if warned of the risk of paralysis on the basis that the "legal cause" of the neurapraxia could never be the failure to warn of another risk that did not materialise.

Court of Appeal

On appeal to the Court of Appeal before Allsop P, Beazley and Basten JJA, Mr Wallace argued that Harrison J erred in holding that the legal cause of the neurapraxia could not be the failure to warn of the risk of paralysis. The Court of Appeal tested that argument by assuming that Dr Kam negligently failed to warn Mr Wallace of the risk of paralysis and that, had he been warned of the risk, Mr Wallace would not have undergone the procedure. The question for consideration was then whether, on that assumption, Dr Kam was liable for the neurapraxia. Although the Court was divided in its response to that question, the majority held that he was not liable for the neurapraxia.

The High Court

In a unanimous decision, the High Court upheld the decision made by the majority of the Court of Appeal. The critical issues considered by the Court were Dr Kam's duty of care and causation.

Dr Kam's duty of care

The High Court confirmed previous authority (Rogers v Whitaker (1992) CLR 479) that the common law duty of a medical practitioner to a patient is a single comprehensive duty to exercise reasonable care and skill in the provision of professional advice and treatment. A component of that duty is an obligation to warn a patient of "material risks" of physical injury in a proposed treatment. A risk is material if it is a risk to which a reasonable person in the position of the patient would be likely to attach significance or a risk to which the medical practitioner knows or ought reasonably to know that a particular patient would be likely to attach significance in choosing whether or not to undergo treatment. This component of the duty reflects the patient's right to choose, as well as the need to be adequately informed in order to make that choice rationally.

The High Court noted that the common law duty owed by a medical practitioner to a patient is ordinarily breached where the medical practitioner fails to exercise reasonable care and skill to warn a patient of any material risk of physical injury inherent in a proposed treatment. However, the compensable damage is not impairment of the right to choose or exposure of the patient to an undisclosed risk. Instead, the compensable damage is limited to the actual occurrence and consequences of physical injury sustained by the patient as a result of the medical treatment following their choice to undergo that treatment.

On this basis, the High Court held that Dr Kam breached his common law duty by failing to warn Mr Wallace of the two material risks inherent in the procedure.

Causation

Having found against Dr Kam on the issue of breach, the Court also held against Mr Wallace on causation. In making this determination, the High Court noted that the relevant test involved the consideration of two questions in accordance with s 5D of the Civil Liability Act 2002 (NSW):

a factual question - whether the harm suffered by Mr Wallace would have occurred absent Dr Kam's negligence (per s 5D(1)(a)); and

a normative question - whether it is appropriate for the scope of the Dr Kam's liability to extend to the physical injury in fact sustained by Mr Wallace in circumstances where Mr Wallace would not have chosen to undergo the surgical procedure had he been properly warned of all material risks but would have chosen to undergo the surgical procedure had he been warned only of the risk that in fact materialised (per s 5D(1)(b)).

In considering the first question, the High Court stated that factual causation is established if the patient proves, on the balance of probabilities, that he or she sustained, as a consequence of deciding to undergo the medical treatment, physical injury which he or she would not have sustained if warned of all the material risks. Because the determination of factual causation turns on an assessment of what the patient would have done had the medical practitioner warned of all material questions, the determination is governed by s5D(3). What the patient would have done if warned is to be determined subjectively but evidence of what he or she would have done is inadmissible by virtue of s5D(3)(a), except to the extent that the evidence is against the interests of the patient.

In considering the second question with respect to the scope of Dr Kam's liability, the High Court noted that a limiting principle of the common law is that the scope of liability in negligence normally does not extend beyond liability for the occurrence of harm, the risk of which it was the negligent party's duty to exercise reasonable skill and care to avoid. In this regard, the scope of liability of breach of a duty to exercise reasonable care and skill to avoid foreseeable harm does not extend beyond harm that was foreseeable at the time of breach. Accordingly, the Court emphasised that a medical practitioner will not be liable to a patient for physical injury that represents a materialisation of risk which is beyond the duty of that medical practitioner to warn.

The High Court noted that the present facts concerned the materialisation of one of a number of distinct risks of different physical injuries. Their Honours emphasised that the scope of liability needs to reflect the underlying policy designed to protect the patient from the occurrence of physical injury, the risk of which is unacceptable to the patient. The liability does not extend to harm from risks that the patient was willing to hazard, whether through express choice or if the disclosure had been made.

The conclusion reached was that Dr Kam was not liable to Mr Wallace for impairment of Mr Wallace's right to choose whether or not to undergo the surgical procedure and was not liable to Mr Wallace for exposing him to an unacceptable risk of catastrophic paralysis. He could only be liable for the neuropraxia which Mr Wallace sustained. However, Mr Wallace's position with respect to the neuropraxia, when considered for the purposes of causation, is in principle no different from what it would have been had Dr Kam warned him of the risk of neuropraxia and had he made an express decision to proceed with the surgery in light of that warning. The Court emphasised that Mr Wallace ought not to be compensated for the occurrence of physical injury, the risk of which he was prepared to accept. Given Mr Wallace's willingness to accept the risk or the neurapraxia, any failure of Dr Kam to warn Mr Wallace of the risk of paralysis could not be the "legal cause" of the neurapraxia that ultimately materialised.

The effect of the decision is to significantly limit the scope of future failure to warn cases, as the High Court has made it clear that such claims can only succeed where the risk of which the doctor should have warned is that which ultimately comes home for the patient.