In NSW, Section 5O of the Civil Liability Act provides a defence to a doctor or health professional who is defending a negligence claim.
Under s 5O, a person will not be liable “if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice”.
S 5O is often regarded as re-introducing a version of the Bolam test, since the standard of care required of a professional person is ultimately determined by the practices of his or her peers.
In Dobler v Halverson, the NSW Court of appeal clarified how s 5O operates. It pointed out that in a medical negligence case, both parties will call expert evidence to attempt to demonstrate that what the defendant did fell short of – or did not fall short of – acceptable professional practice .
According to the Court, the effect of s 5O is that if the court finds the doctor’s conduct was in accordance with “professional practice regarded as acceptable by some” in the profession, then (subject to the court considering professional opinion to be irrational), that professional practice will set the standard of care and the plaintiff patient will therefore fail: .
Sparks v Hobson; Gray v Hobson
Understanding about the scope of s 5O has been thrown into disarray by the NSW Court of Appeal in Sparks v Hobson; Gray v Hobson  NSWCA 29 (1 March 2018).
The facts are complex. Mr Hobson suffered from Noonan Syndrome, a genetic disorder that resulted in serious curvature of his spine and a reduced chest cavity that prevented his left lung from filling with air. This caused breathlessness and restrictive airways disease. He underwent surgery that was intended to strength his spine and relieve pressure on the chest cavity.
The first stage of the operation was uneventful; however, the second stage was brought forward because Mr Hobson was in intensive care due to pneumonia in his left lung and the obstruction of his left airway. The second stage of the operation required Mr Hobson to lie face down on the operating table, while screws were placed in his spine.
The position of Mr Hobson during the operation, and the placing of the screws, created further pressure on the chest wall, further restricting his breathing.
Mr Hobson was regarded by the expert witnesses as presenting a “very unusual and difficult anaesthetic challenge due to the significant compression of his left main bronchus by his spine and due to the requirement for prone positioning during surgery” 
The operation began at 7pm on 17 November 2009. The level of carbon dioxide in Mr Hobson’s blood rose during the surgery, and at 9.30pm, Dr Sparks administered a drug called vecuronium to try to improve ventilation. It led to no improvement; also, vecuronium was a muscle relaxant, and it meant that spinal cord monitoring was thereafter ineffective. From that point onwards, Dr Sparks could only be guided by the oxygen and blood pressure readings “as his criteria for stopping the operation” .
Dr Sparks described Mr Hobson’s high blood carbon dioxide level, at 8.30 to 8.35pm as “very serious”. He had what the clinicians called “profound respiratory and metabolic acidosis”. At 8.50, Dr Sparks made two telephone calls to two colleagues (Dr Barratt, an anaesthetist, and Dr Marshman, a cardiothoracic surgeon), but they were unable to make any further suggestions about how to reduce the risk of cardiovascular failure.
At around 9.25pm, Mr Hobson’s blood pressure and oxygen levels dropped dramatically, and at Dr Spark’s request, the wound was closed rapidly and the operation terminated.
One of the issues in dispute was whether Dr Sparks should have terminated the operation at a time earlier than he did. There was evidence that due to respiratory collapse around 9.30pm, precipitated by obstruction of circulation (causing lack of oxygen), irreparable damage was done to Mr Hobson’s spinal cord, leaving him a paraplegic.
Although the surgery was later completed successfully, Mr Hobson’s paraplegia remained.
The trial judge found against both Dr Sparks, and the principal surgeon, Dr Gray.
On appeal, the Court of Appeal unanimously allowed Dr Gray’s appeal. However, Dr Sparks’ liability was upheld by a majority of 2:1.
The Court of Appeal’s decision in Sparks v Hobson raises a number of issues relating to the interpretation of provisions in the Civil Liability Act.
This post focuses specifically on the court’s interpretation of the defence in s 5O.
The uncertainty introduced by the irreconcilable judgments of the Court of Appeal in Sparks v Hobson is so significant that it will be a great shame if leave to appeal to the High Court is not granted.
In McKenna v Hunter & New England Local Health District  NSWCA 476, Macfarlan JA pointed out that the defence in s 5O is premised on the defendant doctor demonstrating that they conformed with “a practice that was in existence at the time the medical service was provided” and secondly, that the “practice was widely although not necessarily universally accepted by peer professional opinion as competent professional practice”: .
This emphasis on the existence of a “practice” – in the sense of a pattern of response by medical practitioners to a clinical scenario, is in contradistinction to there simply being a widespread view among peers that what the defendant did in the circumstances of the case constituted “competent professional practice”.
The significance of the need for a “practice”, as suggested by Macfarlan JA, is that in an unusual case, there may be no relevant practice in existence that the defendant doctor can identify and appeal to for the purposes of a defence.
In Sparks v Hobson, Basten JA rejected the suggestion in McKenna that the defence in s 5O only applies where the defendant can identify “a regular course of conduct adopted in particular circumstances” .
McKenna was overturned by the High Court, so Basten JA thought that the reasoning of the majority of the Court of Appeal, on the interpretation of s 5O, was no longer binding: 
He said: “there is no grammatical or semantic difficulty in describing an argument run by counsel in a novel case as demonstrating competent or incompetent professional practice” .
In a novel case, Basten JA thought that a defendant may invoke the defence in s 5O “by reference to how an assessment of the circumstances (which may be unique) would be undertaken by a knowledgeable and experienced practitioner” .
Although Basten JA did not think a defendant needed to establish they acted in accordance with a “practice” (understood in the sense of an established course of conduct followed in the circumstances of the case), he nevertheless concluded that Dr sparks had failed to establish a standard, widely accepted in Australia, of competent professional practice, for the purposes of availing himself of the s 5O defence.
In Sparks v Hobson, Macfarlan JA reiterated his approach in McKenna. He said: “It is not enough that experts called to give evidence consider that the conduct was reasonable and that it would have been so regarded by other professionals if they had been asked about it at the time of the conduct” .
In this case, the surgery was highly unusual. Although the expert witnesses all agreed Dr Sparks acted reasonably in the actions he took during the operation, and although they considered professional peers would likely have taken the same view, the experts and the defendant did not point to an established practice that was followed by Dr Sparks in the circumstances of the case .
In Macfarlan JA’s analysis, this was fatal to Dr Sparks’ defence: see .
The third justice in the NSW Court of Appeal was Simpson JA, who considered that she was bound to accept the construction of s 5O adopted in the McKenna case.
But for the constraint of precedent, Simpson JA would not have adopted the approach of Macfarlan JA.
She said: “As construed in McKenna, s 5O can apply only in limited circumstances, where the defendant can, or seeks to, identify a discrete practice to which he or she conformed. It necessarily excludes unusual factual circumstances, such as occurred in McKenna, and such as occurred in the present case. It does not appear to me that s 5O was intended to have such limited application. However, as I have said, I consider myself constrained to follow and apply that decision” .
In Justice Simpson’s view, Dr Sparks failed to establish a defence based on s 5O because he could not identify a “practice” to which he conformed in the highly challenging and unusual circumstances of the case. This, “notwithstanding that the overwhelming medical evidence was that his conduct was in accordance with what was widely accepted in Australia as competent professional practice’” .
Despite this, Simpson JA found in favour of Dr Sparks because she thought that in the circumstances of the case, s 5I applied.
S 5I provides that a person is not liable for the materialisation of an inherent risk that cannot be avoided by the exercise of reasonable care and skill.
In her Honour’s view, once it was found that Mr Hobson’s deteriorating condition warranted the surgery “as emergency surgery”, and that the surgery carried the risk of paraplegia, s 5I applied to excuse Dr Hobson from liability.
In addition, Simpson JA concluded that the evidence did not establish that the failure by Dr Sparks to terminate the operation before 9.30pm amounted to a departure from the standard of reasonable care and skill required of a specialist anaesthetist , given that Mr Hobson “needed urgent surgery to ensure his survival”: .
The future of the s 5O defence
As things stand, the judgments of Justices Macfarlan and Simpson in Sparks v Hobson give majority support to an interpretation of s 5O that limits its scope as a defence for doctors in medical negligence proceedings.
The issue at stake goes to the heart of what the defence requires courts to do.
In the view of Justice Simpson, the task of the court when considering the defence in s 5O is not to choose between competing views but to determine whether as a factual matter, the acts and/or omissions of the defendant that give rise to allegations of breach of duty of care “had the acceptance of peer opinion, even if other peer opinion was different”: .
This view is consistent with the assumption that s 5O was intended to introduce a version of the Bolam principle into New South Wales law, thereby ensuring that medical practices, rather than a court, ultimately define the standard of care by which a doctor’s conduct will be judged.
If the view of Justice Macfarlan is followed, by contrast, the role of the court would focus on determining whether a relevant “practice” exists on which a defence might be founded.
In cases where no such practice exists, s 5O can have no application.
The question of standard of care and breach would then fall to be determined by the court, applying common law principles, “guided by the evidence of medical practitioners skilled in the area of medical practice in question” , and altered (to the extent that it is altered) by the principles set out in 5B [see  per Simpson JA].
So, on what basis did the majority Justices consider that Dr Sparks had breached his duty of care?
Justices Basten and Macfarlan held against Dr Sparks.
According to Justice Macfarlan, Dr Sparks’ failure to terminate the operation was not limited to a short period of time, but extended for at least 20 minutes after the two telephone calls to Dr Barratt and Dr Marshmann until 9.25pm, when Mr Hobson’s blood pressure and oxygen level dropped. By then the damage had been done.
Essentially, Justice Macfarlan thought the breach of duty was made out because Dr Sparks unreasonably ignored a “serious and imminent intra-operative danger” (the high carbon dioxide levels) when the other countervailing risk (the risk to Mr Hobson if the operation was terminated) did not have the same immediacy: .
Also, “Dr Sparks had to assess and respond to the immediate danger to Mr Hobson (rather than the more remote risks that could eventuate if the operation was not completed) because Dr Sparks’ duty as principal anaesthetist was to protect the patient’s well-being whilst the operation was in progress” .
Justice Basten agreed that the decision to allow the operation to continue for so long, after he had sought help from experienced colleagues, without success, was more than just an “erroneous clinical judgment” but was a breach of his duty of care to Mr Sparks .