Causation in failure to warn cases

Yesterday the High Court delivered judgment in Wallace v Kam, and important case addressing causation in the context of a failure to warn by a medical practitioner.

Mr Wallace sought medical assistance in relation to a condition of his lumbar spine. Dr Kam, a neurosurgeon, performed a surgical procedure on him. The surgical procedure had inherent risks. One risk was of temporary local damage to nerves within his thighs, described as "bilateral femoral neurapraxia", resulting from lying face down on the operating table for an extended period. Another, distinct risk was a one-in-twenty chance of permanent and catastrophic paralysis resulting from damage to his spinal nerves. The surgical procedure was unsuccessful: the condition of Mr Wallace's lumbar spine did not improve. The first risk materialised: Mr Wallace sustained neurapraxia which left him in severe pain for some time. The second risk did not.

Mr Wallace claimed damages from Dr Kam for the neurapraxia he sustained. Mr Wallace's claim in the Supreme Court of New South Wales was that Dr Kam negligently failed to warn him of risks including the risk of neurapraxia and the risk of paralysis and that, had he been warned of either risk, he would have chosen not to undergo the surgical procedure and would therefore not have sustained the neurapraxia.

The trial judge found that Dr Kam negligently failed to warn Mr Wallace of the risk of neurapraxia. But he also found that Mr Wallace would have chosen to undergo the surgical procedure even if warned of the risk of neurapraxia.  Because it was that risk which actually materialized, the question of whether Dr Kam had negligently failed to warn Mr Wallace of the risk of paralysis was irrelevant.

In the Court of Appeal Allsop P and Basten JA held that even if Dr Kam negligently failed to warn Mr Wallace of the risk of paralysis and that, if warned of that risk, Mr Wallace would not have undergone the surgical procedure, nonetheless he was not entitled to damages for the neurapraxia.  Beazley JA held to the contrary, noting that had he been warned of the risk of paralysis, the surgery (and hence the neurapraxia) would not have occurred.

The High Court unanimously rejected Mr Wallace’s appeal.  The Court held that the question of liability for the neurapraxia was to be answered by application of section 5D of the Civil Liability Act 2002.  That section divided the causation issue into two elements:  factual causation (ie was the negligence was a necessary condition of the occurrence of the harm - a straightforward “but for” test) and scope of liability (ie is it appropriate for the scope of the negligent person's liability to extend to the harm so caused).

The High Court held that a medical practitioner’s duty of care was a single comprehensive duty to exercise reasonable care and skill in the provision of advice and treatment.  A component of that single duty of care is to warn a patient of “material risks” inherent in a proposed treatment.  On the assumptions being made for the purposes of deciding the case, that duty was breached by the failure to warn of the risk of paralysis and the neurapraxia, and had Mr Wallace been warned of the risk of paralysis he would not have undergone the surgery.

In this case, the factual causation question was clearly and straight-forwardly answered in the affirmative.  The failure to warn of the risk of paralysis was a necessary condition of the neurapraxia sustained by Mr Wallace.

More difficult, however, was the “scope of liability” question.  The duty of a medical practitioner to warn the patient of material risks inherent in a proposed treatment is imposed by reference to the underlying common law right of the patient to choose whether or not to undergo a proposed treatment.  Beazley JA had considered it was appropriate to impose liability in this case because to do so would promote that objective.  However, the High Court held that the policy underlying the requirement that a doctor exercise of reasonable care and skill in warning of material risk is neither to protect that right to choose nor to protect the patient from exposure to all unacceptable risks. The underlying policy is rather to protect the patient from the occurrence of physical injury the risk of which is unacceptable to the patient. It is therefore appropriate that the scope of liability for breach of the duty reflect that underlying policy.  Accordingly, in terms of section 5D, it was not appropriate for the scope of liability to extend to the harm (neurapraxia) that Mr Wallace was willing to accept asa consequence of the surgery.

The position of Mr Wallace in respect of the neurapraxia when considered for the purposes of causation was in principle no different from what his position would have been had Dr Kam properly warned him of the risk of neurapraxia and had he made an express choice to proceed with the surgical procedure in light of that warning. He was not to be compensated for the occurrence of physical injury the risk of which he was prepared to accept.