Sally Clark

Sally Clark 1964-2007

Sally Clark

Statements from experts on Statistics

Roy Meadow, an expert witness for the prosecution said the chance of a double cot death in Sally's family was a "vanishingly small" one in 73 million.
What a professor of statistical science at Oxford University says:
Peter Donnelly: 'It is poor science. It's not rigorous, it's just wrong.' Donnelly points out that a key issue is whether Meadow was right to multiply the risk factors of the two cot deaths to get to the one in 73 million number. 'It is only valid to multiply the numbers if it has been established whether or not one child dying of cot death is completely independent of whether or not another has died. In order to present that kind of number in court one should have evidence to establish that independence.'
What the Royal Statistical Society says:
On Tue 23/10/01 , the Royal Statistical Society issued this press release expressing its concern about this misuse of statistics.
What Peter Fleming, the author of the article in which Roy Meadow found the 73-million-to-one figure says:
Peter Fleming, professor of child health at Bristol University: 'This statistic was never intended as an estimate of real risk. It was never meant to suggest that this was an unnatural occurrence. This statistic is of no relevance to a jury trying to understand whether babies had died naturally or unnaturally. It was used completely out of context and so, without explaining how it was arrived at, it is potentially misleading and dangerous.'
Dr Watkins, director of Public Health at Stockport Health Authority, writes in the British Medical Journal:
"It is speculation whether Sally Clark would have been acquitted without this evidence. But with this mathematical error prominent, the conviction is unsafe.
If statistics like this continue to be used in criminal cases, miscarriages of justice will occur and this may have been one. I can say that this particular evidence was wrong."
[From the Daily Telegraph, 31 December 1999]

Further reading

1. Reese A. In Statistics and justice. Accessed November 1999.
2. Peterson DR, Subotta EE, Dubing JR. Infant mortality among subsequent siblings of infants who died of sudden infant death syndrome. J Pediatr 1986; 108: 911-914[Medline].
3. Oyen N, Skjaerven R, Jurgens LM. Population-based recurrence risk of sudden infant death syndrome compared with other infant and foetal deaths. Am J Epidemiol 1996; 144: 300-305[Abstract].
4. Guntheroth VG, Lohmann R, Spiers PS. Risk of sudden infant death syndrome in subsequent siblings. J Pediatr 1990; 116: 520-524[Medline].
5. Irgens LM, Skjaerven R, Peterson DR. Prospective assessment of recurrence risk in sudden infant death syndrome siblings. J Pediatr 1984; 104: 349-351[Medline].
6. Froggart P, Lynas MA, McKenzie G. Epidemiology of sudden unexpected death in infants ("cot death") in Northern Ireland 1971. Br J Soc Prev Med 1984; 25: 119-134.
7. Beal SM, Blundell HK. Recurrence incidence of sudden infant death syndrome. Arch Dis Child 1988; 63: 924-930[Abstract].
8. Emery JL. Families in which two or more cot deaths have occurred. Lancet 1986; i: 313-315.
9. Wolkind S, Taylor EM, Waite AJ, Dalton M, Emery JL. Recurrence of unexpected infant death. Acta Paediatrica 1993; 82: 873-876[Medline].
This Bibliography is from the Article by Watkins in BMJ.

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