Peer Professional Opinion and Inherent Risk considered by the NSW Supreme Court in the recent case of Polsen v Harrison (No. 8)

  • 7 Aug 2023

A recent Supreme Court of NSW judgment in the matter of Katrina Polsen v Dr Harrison (No.8) (‘Polsen’) considers the pleading of Inherent Risk and Competent Professional Practice under the Civil Liability Act 2002 NSW (‘the Act’) and the viability of expert evidence based on assumptions which are not supported by evidence.

Key Points
  • A pleading of section 5O pursuant to the Act provides a complete answer to the plaintiff’s claim. When successfully established, there is no need to consider sections 5B, 5C or 5D of the Act.

  • A pleading of section 5I should be considered when the complications affecting the plaintiff, both intra-operatively and post-operatively, were inherent risks of the procedure.

  • It is essential that all experts receive identical assumptions and information for the purposes of the conclave. Expert opinion based on assumptions will be disregarded in the absence of supportive evidence


Background to Polsen’s Case

On 22 July 2013, Katrina Polsen (‘the plaintiff’) underwent a sleeve gastrectomy (‘the procedure’), to manage her morbid obesity, performed by Dr Harrison, surgeon (‘the defendant’). Post-operatively, the plaintiff had a complex recovery involving many admissions to hospital and further surgical procedures due to intermittent sepsis and malnutrition, among other things, over a period of five years.

It was alleged that, due to the negligence on the part of Dr Harrison in his performance of the procedure and his subsequent treatment, the plaintiff had been left unable to work and that her capacity to enjoy life had been significantly diminished.

The plaintiff’s claim was brought on the following basis:

  1. Given the plaintiff’s co-morbidities, alcohol abuse and liver dysfunction, she should have been counselled and the elective surgery, which was not urgent, should have been delayed by the defendant. Alternatively, the plaintiff claims that the defendant did not properly warn her of the risks associated with the procedure, and if he had, she would not have opted to proceed.

  2. The plaintiff’s alternative case was that the defendant’s initial management and technical performance of the procedure was negligent, and that said negligence contributed to a gastric leak at the site of the surgery, causing ongoing illness which necessitated further surgeries. As part of this case, the plaintiff also alleged that the defendant had failed to detect that she had a gastric leak (more correctly, a staple line leakage) for a prolonged period and that he had failed to refer her to a tertiary facility for appropriate treatment.

In response the plaintiff’s claim, the defendant maintained that his treatment was not negligent in that he took appropriate steps to address the risk of harm pursuant to section 5B the Act and that he was not liable in negligence because he acted in a manner that was widely accepted in Australia by peer professional opinion as competent professional practice, as per section 5O of the Act. He also claimed that the plaintiff’s complications and post-operative course were consistent with the inherent risks of the procedure, and on this basis, he was not liable under section 5I of the Act. 

The Supreme Court Decision (Lonergan J)

Her Honour, Justice Lonergan conducted a thorough analysis of the clinical and expert evidence marshalled by the parties. Firstly, her Honour concluded that it could not be established how much alcohol the plaintiff was drinking in the lead up to the procedure due to the inconsistent accounts she provided. Lonergan J also found that the defendant’s surgical approach and technique was appropriate, and that the plaintiff was a suitable candidate for the procedure.

Ultimately, her Honour found in favour of the defendant, based on the following findings:

  1. The defendant acted in a manner that, at the material time, was widely accepted as competent professional practice by his surgical peers, thereby validating his pleading of section 5O of the Act. This was established on the opinion of the defendant’s bariatric experts, Professor Wendy Brown and Dr Garrett Smith.

  2. The pleading of 5O, when successfully established, provides a complete answer to the claim, as opposed to a defence once negligence is established. Therefore, there was no need to consider sections 5B and 5C of the Act.

  3. Factual causation, pursuant to section 5D of the Act, was not proven, however, given the finding of 5O, there was no need to address this issue.

  4. The complications experienced by the plaintiff post-operatively were within the inherent risks of the procedure, of which she was warned. There was no failure on the part of the defendant in this respect. Section 5I of the Act was established.

  5. The experts qualified by the plaintiff formed their respective expert opinions on assumption that the plaintiff was drinking one bottle of wine per night, as opposed to a glass, which is recorded in the contemporaneous record. It is essential that, for the purposes of the conclave, all experts need to be provided with identical assumptions and information.


Polsen’s case provides insight into the Court’s position with respect to the pleading of sections 5O and 5I of the Act. The case further emphasises that pleading of section 5O of the Act, when established, provides a complete answer to the plaintiff’s claim, as opposed to a defence to a finding in negligence. Further, this decision highlights that, when appropriate, section 5I of the Act should be pleaded, even in complex cases where the ‘inherent risks’ evolve over an extended period.

Blog written by Hicksons’ Partner, Emma Ellis, and Associate, Ashley McIntyre.

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