Williams V Bermuda Hospitals Board (2016) UKPC 4


The Privy Council of the United Kingdom has affirmed that in order to succeed on causation in a medical negligence claim where there are cumulative causative factors, a claimant needs not prove the negligent act was, on the balance of probabilities, the cause of the injury, but must show that the negligence made a material contribution to the injury.

Accordingly, defendants will be unable to sustain a defence on causation where a negligent act or omission materially contributes to the overall process of harm to the patient, for example in cases involving a delay in diagnosis of cancer or negligent management of labour, even if the claimant cannot show that the breach of duty alone, on balance, caused the injury.

However, if the injury is “divisible”, as opposed to cumulative or indivisible, defendants will only be liable for the part of the injury which they actually caused. Therefore if a certain aspect of the patient’s injury would have been sustained in any event, it is open for defendants to argue that they should not be liable for that aspect of the claim. 

Whilst the Privy Council’s decision is no longer binding on the Hong Kong courts, as the court of final appeal for several commonwealth countries, it will be highly influential and we will wait to see if the Hong Kong courts will follow this decision. 


The patient attended the Hospital Board’s Accident and Emergency department complaining of abdominal pain. A CT scan was ordered but there was an avoidable delay before it was performed and an appendectomy was undertaken. At the operation it was found that the appendix had ruptured and there was widespread pus throughout the pelvic region, with phlegmon around the liver and cecum. The accumulation of pus resulting from the ruptured appendix led to myocardial ischaemia. In addition, the patient suffered lung complications, requiring life support in the intensive care unit. The court had to determine whether the negligent delay in arranging the CT scan had caused the myocardial ischaemia.

The trial judge held that there had been a negligent delay, but the patient had failed to prove causation on the balance of probabilities in relation to the myocardial ischemia. He awarded modest damages to the patient for his additional pain and suffering only.

The Bermuda Court of Appeal overturned that ruling, with Ward JA’s judgment stating that the trial judge was in error by “raising the bar unattainably high” in his findings that the patient had failed to prove his case. Ward JA held that there had been “numerous delays” (both negligent and non-negligent), which had contributed materially to the injury, increasing damages from US$2,000 to US$60,000. Ward JA, referencing Bailey v Ministry of Defence [2009] 1 WLR 1052, stated that the but for test is sometimes relaxed to enable a claimant to overcome the causation hurdle when it might otherwise seem unjust to require the claimant to prove the impossible. Ward JA added that the question of causation is no longer a question of all or nothing, but one of sufficiency.


The Hospital Board appealed but the Privy Council of the United Kingdom rejected the Hospital Board’s submissions that the material contribution principle only applied to simultaneous contributory causes, stating that whilst the sequence of events may be highly relevant to considering whether, as a matter of fact, a later event had made a material contribution to the outcome, "as a matter of principle successive events are capable of each making a material contribution to the subsequent outcome.”

The Privy Council noted that the trial judge had found that injury to the heart and lungs was caused by a single known agent, namely sepsis from the ruptured appendix, which developed incrementally over a period of approximately six hours, progressively causing myocardial ischaemia. The sepsis was not divided into separate components causing separate damage and its development was a single continuous process, during which the sufficiency of the supply of oxygen to the heart steadily reduced. The Privy Council concluded, on the balance of probabilities, that the negligent delay “materially contributed to the process, and therefore materially contributed to the injury to the heart and lungs.” The Hospital Board’s appeal was therefore dismissed.