Loss of chance

24 June 2011

Dimitra Dubrow, Principal

Last year, the High Court delivered a very important decision about the 'balance of probabilities' standard, which was tested in the case of Tabet v Gett.

Tabet v Gett

Tabet was a case about the delayed diagnosis of a brain tumour in a young girl and the effect of that delay on her severe brain damage. The judge hearing the case decided that there was a 40 per cent (less than even) chance that the girl would have avoided 25 per cent of the brain damage had the tumour been diagnosed in an appropriate timeframe, which was about 24 hours before the actual diagnosis was made. Over that 24 hour period, the girl's condition worsened, her raised intracranial pressure was not treated and she suffered a seizure.

The case was appealed all the way to the High Court. The court did not agree with the judge and confirmed the 'balance of probabilities' test of causation, that is, the need to show that the negligence more likely than not caused the injury or medical condition. The court said it was not enough to show that there was a chance - such as a 40 per cent chance - that the outcome would have been better. Rather, it had to be shown that diagnosis of the brain tumour a day earlier would have more likely than not avoided 25 per cent of the brain damage. The court was not prepared to change the law and 'lower' the test for causation.

Implications of High Court decision

The decision has a number of implications for medical law claims, especially ones involving progressive illnesses, for example, where a doctor unreasonably fails to act on a patient's symptoms which leads to a delayed diagnosis of cancer. In those cases, it can sometimes be hard to work out what part of the condition would have been avoided with timely treatment. Because of the court's decision, it is important that medical evidence focus on the likely or probable difference and not on possibilities or lost chances.