Probability and proof – the legal versus the medical – legal wins!

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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