Sally Clark: Trial and error by Judge and Jury

Area of Science:

• Forensic Statistics
• Legal Procedure
• Criminal Justice

Background:

• The 1999 Sally Clark conviction for infant murder relied heavily on statistical evidence.
• Professor Sir Roy Meadow's estimate suggested a 1 in 73 million probability of two natural sudden infant deaths in one family.

Purpose of the Study:

• To examine methodological limitations in the statistical evidence used in the Sally Clark case.
• To analyze the broader implications for the admission and interpretation of expert evidence in criminal trials.
• To compare English court procedures with the Daubert standard in the United States.

Main Methods:

• Analysis of three key methodological limitations in the prosecution's statistical estimate.
• Examination of the evidential process concerning probabilistic evidence in the Clark trial.
• Review of English criminal court approaches to expert evidence and subsequent legal developments.

Main Results:

• The statistical estimate was methodologically flawed, distorting comparative inference and causal determination.
• Sudden Infant Death Syndrome (SIDS) as a diagnosis of exclusion limits the certainty of population frequency data.
• The probability estimate lacked context regarding competing explanations, diminishing its interpretive value.

Conclusions:

• The Sally Clark case exemplifies a miscarriage of justice due to flawed statistical evidence and its interpretation.
• English courts require improved frameworks for scrutinizing and contextualizing expert probabilistic evidence.
• Subsequent legal reforms and comparisons with the Daubert standard indicate ongoing challenges in managing expert evidence.