Odds boost for Clark

The Royal Statistical Society has cast further doubt over the conviction of solicitor Sally Clark and expressed its concern at the misuse of statistics in court.Clark was convicted of the murder of her two baby sons after a medical expert declared that the chance of two children in the same family suffering from sudden infant death syndrome (SIDS or cot death) was one in 73 million.This was reached by squaring the odds of one death happening, which does not take into account the possibility of genetic or environmental reasons which may make a second case within the same family much more likely.

'This approach is, in general, statistically invalid,' said the society.

'It would only be valid if SIDS cases arose independently within families, an assumption that would have to be justified empirically.'The one in 73 million figure is thought to have had a major influence on the outcome of the case.The statement continued: 'Society does not tolerate doctors making serious clinical errors because it is widely understood that such errors could mean the difference between life and death.

The case of R v Sally Clark is one example of a medical expert witness making a serious statistical error, one which may have had a profound effect on the outcome of the case.'