A recent illustration of the difference between proof in the legal and medical contexts was given in Bell v Ashford & St Peter’s Hospital NHS Trust (QBD 27 July 2016).

A patient had oesophageal cancer.  During an endoscopy the patient’s tumour was negligently perforated, causing serious infection and delaying chemotherapy to treat the tumour.  The patient subsequently was diagnosed with metastatic disease and died within 4 years.  Prior to the perforation, scans and tests had shown no sign of metastatic disease, no evidence of local or distant disease spread and no sign of lymphatic involvement.

The substantial claim for damages by the patient’s estate, based on the loss of a normal life expectancy following what it was alleged should have been ‘successful’ treatment for the cancer, depended on proof that the metastatic disease was caused by the perforation – that ‘but for’ the perforation, the metastatic disease would not have occurred and the patient would not have died.  In other words, the issue was one of causation.

The Trust argued that the patient probably had metastatic disease before the perforation so that the perforation made no difference with regard to that spread (although it was conceded that some damage – but no significant reduction of life expectancy – was suffered as a result of the delay in treatment caused by the infection).  For the patient’s estate, while the expert was unable to point to the definite mechanism by which the outpouring of tumour cells as a result of the perforation caused the recurrence and increased the risk of more distant spread, the expert considered it probable that it did do so.

The judge concluded that, while acknowledging that there was no scientific certainty on the issue, on the balance of probabilities the perforation did cause the metastatic disease and therefore did cause the patient’s premature death.  There was no evidence of metastatic disease prior to the perforation despite all appropriate investigations, and the perforation was therefore the probable cause.  The claimant had proved its case.

(To read more about the legal concept of causation, its application to claims for damages in injury claims and how the expert should report on it, the reader is referred to Chapter 6 of ‘Writing Medico-Legal Reports in Civil Claims – an essential guide’)

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The recent decision in Williams v Bermuda Hospitals Board [2016] 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[1], 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[2] (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[3], 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.

[1] Hotson v East Berkshire Area Health Authority [1987] AC 750,

[2] Wilsher v Essex Area Health Authority [1988] AC 1074

[3] Bailey v Ministry of Defence [2009] 1 WLR 1062

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