High Court considers failure to warn of risks and causation

Legal Directions

Medical treatments often have multiple material risks which, individually or cumulatively, may dissuade a patient from undergoing the treatment. This decision reinforces the duty of care of a medical practitioner to warn patients of those risks prior to treatment so that patients can chose whether they are prepared to accept them.

The High Court’s decision highlights that the determination of whether a medical practitioner’s breach of duty for failing to warn of material risks is the cause of the actual harm suffered, requires more than the application of a ‘but for’ test.

In determining causation, it is also necessary to consider the actual harm suffered, whether that harm eventuated from a material risk for which a warning should have been given, and whether the risk that eventuated was unacceptable to the patient.

Dr Kam, neurosurgeon, performed surgery on Mr Wallace’s lumbar spine. The surgery had a number of inherent risks, including  temporary local damage to nerves within the thighs and a 5% chance of permanent paralysis resulting from damage to the spinal nerve.

The surgery was unsuccessful: Mr Wallace’s condition did not improve and he sustained nerve damage which left him in severe pain for a period of time.

Mr Wallace commenced a claim against Dr Kam seeking damages for breach of duty in failing to warn him of two material risks of the operation, namely the risk of the nerve damage that eventuated, and a 5% risk of permanent paralysis resulting from damage to his spinal nerves that did not materialise.

Mr Wallace said that had he been warned of those risks, he would have chosen not to undergo the surgical procedure.

Trial decision

Mr Wallace’s claim did not succeed at trial in the New South Wales Supreme Court. Harrison SCJ, determined that Dr Kam breached his duty of care by failing to warn Mr Wallace of the risk of nerve damage. However, he found that Dr Kam’s negligence was not the ‘legal cause’ of the nerve damage that materialised because Mr Wallace would have chosen to undergo the surgery even if warned of that risk.

The trial judge did not make any finding about the failure to warn of the risk of paralysis because he considered the failure to warn of a risk that did not materialise could not be the ‘legal cause’ of the nerve damage.

Court of appeal

On appeal to the New South Wales Court of Appeal, Mr Wallace argued that the trial judge erred in holding that the failure to warn of the risk of paralysis could not be the legal cause of the nerve damage when, if that warning of paralysis had been given, Mr Wallace would not have had the surgery.

The Court of Appeal proceeded on the assumption that Mr Wallace would not have undergone the surgery if warned of the risk of paralysis. However, the majority of the Court of Appeal considered that there needed to be a causal relationship between Dr Kam’s failure to warn of the risk of paralysis (the breach of duty) and the harm actually suffered by Mr Wallace. The majority determined that the risk of paralysis and the risk of nerve damage were distinct and not related in any way; the risk of paralysis was associated with the skill and care exercised by the surgeon, whereas the risk of nerve damage arose from the way the patient had to lie during the procedure.

Accordingly, the majority decided that it was not appropriate to hold Dr Kam liable for the nerve damage on the basis of negligence relating to a separate risk which did not materialise.

High Court decision

The High Court unanimously agreed with the Court of Appeal’s decision and dismissed Mr Wallace’s appeal.

In reaching this decision, the High Court analysed the operation of section 5D of the Civil Liability Act 2002 (NSW), specifically subsection (1) which provides:

(1)    A determination that negligence caused particular harm comprises the following elements:

(a)    that the negligence was a necessary condition of the occurrence of the harm (factual causation), and

(b)   that it is appropriate for the scope of the negligent person’s liability to extend to the harm so caused (scope of liability).

In the case of a medical practitioner failing to warn a patient of material risks inherent in a proposed medical treatment, the High Court considered that:

  • Factual causation is established if the patient proves that they have sustained, as a consequence of having chosen to undergo the medical treatment, physical injury which the patient would not have sustained if warned of all material risks (this issue turns on a determination of what the patient would have chosen to do if warned of all material risks)
  • Legal causation is established if it is appropriate for the scope of the negligent medical practitioner’s liability to extend to the physical injury in fact sustained by the patient
  • The High Court found that factual causation was established: Dr Kam breached his duty by failing to warn of the two material risks inherent in the surgery and, if warned of all material risks, Mr Wallace would have chosen not to undergo the procedure and would not have sustained the nerve damage
  • In respect of legal causation, the High Court considered that a medical practitioner’s scope of liability for breach of the duty to warn of material risks inherent in a proposed treatment should reflect the underlying policy of that duty, which is to protect the patient from the occurrence of physical injury the risk of which is unacceptable to the patient. The risk of sustaining paralysis was clearly a risk which Mr Wallace was not prepared to accept, as he would not have chosen to undergo the surgical procedure had he been properly warned of that risk. However, the harm actually suffered was not the paralysis, it was the neurapraxia. Therefore, the critical question for the High Court was whether Dr Kam’s liability for failure to warn of the risks extended to a physical injury where, if Mr Wallace had been warned only of the risk that did in fact materialise, he would have chosen to undergo the surgery.

The High Court answered this question in the negative. It considered that it was not appropriate for Mr Wallace to be compensated for the materialisation of a risk that he would have been prepared to accept. Therefore, despite Dr Kam’s breach of duty, he was not liable for exposing Mr Wallace to the unacceptable risk of paralysis where the harm actually suffered resulted from an acceptable risk.

Authored by Nancy Chapman, Senior Associate, Brisbane.


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