Practitioners involved in the area of medical negligence often spend the majority of a case dealing with the issue of causation. From our experience, if there is a breach of duty, it is not that difficult obtaining the necessary expert evidence in support. It is the issue of causation - that the breach has caused a different outcome - that is time consuming and inherently difficult in the majority of cases.

In many cases there can be multiple causes of an outcome. Multiple possibilities are unhelpful to the Plaintiff (and their legal representatives) in a world where the Plaintiff needs to prove probabilities.

In a claim where a Plaintiff was faced with expert evidence advising that there were 6 possible causes for an outcome, many legal representatives would not proceed too far with that claim. Even more so if the potential Defendant was a highly skilled and respected surgeon who had pioneered a certain technique and performed thousands of the operations without complications or claims. Many would say "too hard". But is it? The answer is no but you do need to apply some common sense.

The recent matter of Cox v Fellows1 is a clear example that is it not as hard as you might think.

Material Facts

Professor Cox was a general surgeon with a subspecialty in gastroenterology. He performed a laparoscopic cholecystectomy on Mrs Fellows to remove her gall bladder. As a consequence of that surgery, it was alleged that she suffered a significant stricture to her common hepatic duct.

Ms Fellows was warned of the possible risk of injury to organs near the gallbladder as well as the possible risk of injury to the duct.

Mrs Fellows commenced proceedings against Professor Cox in the District Court of New South Wales for injuries which she alleged were due to Professor Cox misusing the diathermy onto the surgical clips during the procedure. It was alleged that this caused the stricture.

Judgment at first instance

Professor Cox gave detailed evidence of his extensive professional skill and his training in performing these types of procedures and that he had developed techniques for keyhole procedures. He advised the Court that by October 2008, when he performed the procedure on Mrs Fellows that he had performed this same operation approximately 3,800 – 4,000 times and following that surgery he had carried out approximately a further 800 surgeries of this type without complication.

As would be expected, the medical experts called for Professor Cox and Mrs Fellows had conflicting opinions as to what caused the stricture.

McLoughlin DCJ held that Professor Cox breached his duty of care to Mrs Fellows as it was determined that the application of the diathermy occurred at or near the clip on the cystic duct which caused the stricture in the common hepatic duct, that this was a breach of duty because it was a departure from the required standard of care. Consequently Professor Cox was liable to pay damages.  

Professor Cox appealed to the Court of Appeal of the Supreme Court of New South Wales.

The Court of Appeal Decision

The appeal was limited to the issue of liability with two aspects, both involving challenges to the factual findings of the trial judge:

  • Whether on the balance of probabilities a stricture in Mrs Fellows lower common hepatic duct was an injury caused operatively by the deployment of diathermy current during the procedure in the location found by the trial judge; and
  • If so, whether the error of the deployment of the diathermy current by Professor Cox involved a departure from the standard of care required of Professor Cox in the course of the procedure.

With regard to the first issue, Professor Cox argued there were 6 possible causes of the stricture that were as least as likely as the cause found by the trial judge and thus causation had not been established on the balance of probabilities.

The 6 possible causes were: 

  1. A pre-existing condition known as PSC causing multiple strictures;
  2. An idiopathic stricture of unknown aetiology;
  3. The diathermy electrode came into contact with the surgical clip during surgery (which was accepted by the trial judge);
  4. The application of the diathermy in some other position caused the electrical current to travel through the hepatic artery during the surgery (which was an inherent risk that could not be avoided);
  5. The application of the diathermy too close to the bile duct; and 
  6. Some other unknown cause related to the procedure.

Professor Cox abandoned the first cause noted above as he accepted that Mrs Fellow did not have PSC. This left 4 other possible causes of the stricture (excluding cause 3 which was held at trial to have occurred).

The second cause was not accepted by the Court of Appeal as it relied upon the same expert’s opinion who supported the first cause (which had already been abandoned during the appeal) – the opinion being that Mrs Fellows had a pre-existing condition which made her susceptible to multiple strictures.

The fourth cause was not accepted by the Court of Appeal as if that did occur there would have been damage to the hepatic artery which was not the case.

The fifth cause was not accepted as if that did occur there would have been a burn to bile duct which does not cause a stricture.

The sixth cause was not accepted either as there was no evidence that Mrs Fellows had abnormal anatomy nor that Professor Cox experienced any operative difficulties with the anatomy during the procedure.

The remaining issue was whether the third cause, as held at first instance, was correct. The Court of Appeal took into account that the location of the stricture was in the immediate proximity to the surgical clip attached to the cystic duct during the operation, the evidence of Dr Drew which supported the third cause as being the most likely cause and the evidence of Professor Cox at trial when he agreed that the most likely explanation was that the injury occurred during the surgery due to cause number 3 or 4.

The Court of Appeal held that the trial judge was correct to find that the stricture suffered was caused by the diathermy electrode coming into contact with the surgical clip during surgery. That is, causation had been proven by Mrs Fellows.

The remaining ground of appeal by Professor Cox was whether the error of the deployment of the diathermy current involved a departure from the standard of care required of Professor Cox in the course of the procedure. That is, had Professor Cox breached his duty of care?

The Court stated that in relation to the breach of duty the relevant provisions of the Civil Liability Act must be considered.

Section 5B of the Civil Liability Act 2002 (NSW) states that to satisfy the duty to take reasonable care depends upon the:

  1. Considerations of probability the harm would occur;
  2. Likely seriousness of the harm;
  3. Burden of taking precautions to avoid the risk; and
  4. Social utility of the activity that created the risk.

The Court of Appeal accepted that there was a high probability that harm would result if Professor Cox did not take care in the use of the diathermy, that if the harm arose it was likely that anyone who suffered injury as a consequence would suffer harm of a serious nature and thirdly, there clearly was a burden of taking precautions to avoid the risk of harm.

The Court of Appeal then considered whether the risk of injury could have been avoided and scrutinised the evidence given by Professor Cox during the trial.

It was noted that Professor Cox acknowledged during trial that the use of diathermy current is something that you have to be very careful of and "you just don’t do what you shouldn’t do". It was also noted the technique that Professor Cox utilizes was in part, to ensure that this type of injury did not occur. Professor Cox agreed that it was the wrong place to deploy the diathermy if this did occur.

It followed that as the Court had previously held that the injury suffered by Mrs Fellows was due to the diathermy coming into contact with clips, that this could only have occurred due to Professor Cox departing from his usual technique and such a departure was a departure from an acceptable standard of care. The Court also found that the injury would have been avoided if Professor Cox had followed his usual technique.

The appeal was therefore dismissed.


Practitioners faced with multiple possible causes of an outcome must approach the issue of causation with common sense and the nous of determining the probable cause with reference to the facts.

It is not simple nor does it involve certainty. It is time consuming and inherently difficult. However, an assessment of how questions of fact will be determined will go a long way to ensuring you will be able to prove causation.