The recent decision in Williams v Bermuda Hospitals Board  UKPC 4 is an important statement of the principles of the doctrine of ‘material contribution’ in clinical negligence cases. Although it is a Privy Council decision on appeal from Bermuda, the same judges make up the Supreme Court in our jurisdiction, and the decision is effectively binding on the courts of the UK.
Mr Williams had gone to an A&E Department complaining of abdominal pain. He had appendicitis. A CT scan was planned but was not carried out expeditiously. There were significant delays in diagnosing and treating Mr Williams. During the delay, his appendix ruptured and sepsis developed. The sepsis caused myocardial ischaemia.
The judges held that the MI was caused by sepsis of which there was “guilty” sepsis attributable to the negligent delay and “innocent” sepsis which had already begun irrespective of the delay in diagnosis and treatment.
Readers may recall the case of Hotson, the boy who fell from a tree and fractured his femoral epiphysis. There was negligent delay in diagnosis and he developed avascular necrosis. His claim fell because there was a 75% chance of that same outcome in the absence of the negligence and delayed diagnosis, and therefore it could not be proved on the balance of probabilities that the avascular necrosis was caused by the clinical negligence. In Williams however it could not be said that the MI would probably have occurred in any event. Mr Williams succeeded on causation by proving that, on the balance of probabilities, the negligence had materially contributed to the developing sepsis and had therefore materially contributed to the MI.
Williams demonstrates that a defendant’s material contribution need not be concurrent with any non-negligent cause. In Mr Williams’ case, the sepsis attributable to the defendant’s negligence developed after sepsis had already begun to develop. The causes can be either concurrent or consecutive or both. However while the law allows for multiple, cumulative causes it does not allow causation to be established where there are multiple, possible causes, as in the case of Wilsher (multiple possible causes of birth defect, none of which could be shown to be more than 50% probable).
What appears to be a case requiring material contribution in order to be able to establish causation may not be. In Williams it was said that the earlier case of Bailey v MOD, previously considered an example of material contribution, was in fact an example of the ‘egg-shell skull’ principle. The non-negligent condition of pancreatitis in that case was a pre-existing vulnerability on which the subsequent negligent lack of care caused, on the balance of probability, the cardiac arrest.
The medical expert is advised to seek guidance from the instructing solicitor in any case in which traditional causation is unclear and material contribution might be relevant.
 Hotson v East Berkshire Area Health Authority  AC 750,
 Wilsher v Essex Area Health Authority  AC 1074
 Bailey v Ministry of Defence  1 WLR 1062