Articles and Case Studies

The Evolution of Failure to Warn

22 Feb 2013


by Dr Patrick Mahar

Dr Patrick Mahar discusses a recent complex claim which considered the issues of consent and causation.

When considering cases of medical negligence, it must first be established that a doctor owes a duty of care to a patient, and it must be possible for a patient to show that that duty of care was breached. A medical practitioner has a duty to warn a patient of all the material risks inherent in the proposed treatment. Further, in order to establish negligence the Court must be satisfied that the failure to warn was the cause of the harm. An action in negligence will not be successful, however, if the breach of duty cannot be shown to have caused a harm befalling the patient.

Case history

The recent NSW Court of Appeal case, Wallace v Kam,1 visited this issue of establishing causation, whereby a patient suffered a particular harm, and held that the clinician was in breach of his duty of care by not disclosing specific relevant material risks that did not in fact eventuate.

In this case, the patient sought the opinion of a neurosurgeon with regard to management of his back pain, which was caused by a lumbar disc prolapse. The pain had become progressively worse and was limiting the patient's mobility. Conservative measures were initially advised. However, following failure of these, the patient attended a subsequent consultation where the neurosurgeon recommended immediate surgery.

Both the patient and the neurosurgeon agreed that the patient was advised of an approximate 75% chance of improvement of symptoms. The neurosurgeon contended that the patient was consented with respect to an approximately 5% risk of catastrophic paralysis as a result of injury to the spinal cord, however the patient contended he was not. Further, the patient contended that he was not warned about the risk of bilateral femoral neuropraxia.

Following a lengthy operation, the patient awoke with significant pain and paralysis in both legs. Following investigation of these symptoms, the patient was ultimately diagnosed with bilateral femoral nerve neuropraxia as a result of patient positioning, exacerbated by the patient's weight, which was approximately 124 kilograms.

Medico-legal issues

At the initial trial in the NSW Supreme Court, the patient sought damages with respect to the surgeon's failure to warn him of the risk of neuropraxia and 5% risk of paralysis.2 The trial judge held that the surgeon had breached his duty of care in failing to warn the patient adequately with respect to the risk of developing bilateral femoral neuropraxia; however, it was held that the patient did not establish that he would have declined surgery if warned of that risk. The trial judge did not consider the 5% risk of paralysis relevant, as this had not actually eventuated.

At the NSW Court of Appeal, the patient claimed that the surgeon's duty was to warn the patient of all material risks of the operation as a single duty .1 This single duty in this case included being warned of the risk of bilateral femoral neuropraxia, which the patient suffered, as well as the 5% risk of a catastrophic outcome and thus the issue of causation should be determined with respect to a breach of this one "single comprehensive duty". The patient also contended that, was he warned of the risk of catastrophic outcome, he would not have proceeded with the operation at that time and thus would not have developed bilateral femoral neuropraxia.

Causation was not considered to be established in this case by the majority judgment; hence the action in negligence on behalf of the patient was not successful. The Court held that the failure to warn of a particular risk that would have prevented the patient from undergoing surgery but did not occur, does not necessarily result in a finding of negligence in relation to another harm where the risk does occur.


In no way should this judgment reduce the legal obligation of Members to warn patients of relevant material risks prior to undertaking an operation or a procedure. It does, however, suggest that patients cannot, if they suffer a particular adverse outcome, claim in retrospect that they would not have proceeded with a procedure because they were never warned of a risk that did not actually occur. Otherwise a patient would be able to claim compensation for any harm that eventuated if they were able to establish that there was a material risk that was not disclosed which, if disclosed, would have resulted in them not undergoing the procedure. (For more information on Consent see From the President in Defence Update Summer 2012 and the Medico-legal Feature on Consent in Defence Update Winter 2011).

The High Court has recently granted special leave to the patient's solicitor's to appeal the decision of the Court of Appeal.

Dr Patrick Mahar MBBS (Hons), LLB (Hons) is a member of the President's Medical Liaison Council and a MDA National Member.

Summary Points

  • Medical practitioners have a duty to warn patients of material risks prior to undertaking an operation or procedure.
  • An action in negligence will not be successful unless the breach of duty of care, including the duty to warn of risks, caused harm to the patient.

¹ Wallace v Kam [2012] NSWCA 82
² Wallace v Ramsay Health Care Ltd [2010] NSWSC 518

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