"Risk Analysis in the Courts: A Roadmap for Risk Analysts"
Menu of 1998 Full-text Online Casebook
Poster 19
PROOF IN CRIMINAL CASES
CRIMINAL VERSUS CIVIL
Jury
Burden of proof
Remedy
Appeals
HOW RISK ANALYSIS CAN BE USED IN CRIMINAL CASES --(IF AT ALL!!)
Admissibility: DNA
Sufficiency: Because the Constitution guarantees a right to a jury trial in all criminal prosecutions, the sufficiency of risk information is always determined by juries behind closed doors. Nevertheless, there is evidence that juries differ in weighting probabilistic information. The following is a spectrum of jury verdicts using similar DNA evidence:
MISUSE OF PROBABILITY CONCEPTS
People v. Collins, 438 P.2d 33 (Cal. 1968).
The prosecutor sought to persuade the jury, through the testimony of a mathematics instructor, that it was extremely unlikely - in a probabilistic sense - that anyone other than the defendant met the description of the perpetrators of a mugging. Witnesses had testified that the mugging was committed by a black man with a beard and mustache and a white woman with blond hair tied in a ponytail, who escaped in a yellow car. By multiplying the statistical incidences of yellow automobiles, women with ponytails, black men with beards, etc., the mathematician "demonstrated" that the odds were 12,000,000 to 1 that the defendant was not the perpetrator. The California Supreme Court rejected this testimony on several grounds: there was no foundation for the incidence data, the variables were not demonstrably independent (the basis for multiplying them), the variables themselves were not certain, and - most important - the legal system does not assign guilt on the basis of probabilities but rather individual proof. While this case is a criminal case and so subject to more rigorous rules of evidence and proof, it illustrates the discomfort that the judicial system has with "naked" statistical proof - hence the insistence on individual proof in torts cases and the preference for eyewitness medical testimony. [Applegate]
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John Applegate and Wendy Wagner.
Last modified September 27, 2000