The Random Match Probability (RMP) in DNA Evidence: Irrelevant and Prejudicial?
Jurimetrics Journal, Vol. 35, p. 201, 1995
20 Pages Posted: 12 Jul 2009 Last revised: 17 May 2014
Date Written: 1995
The significance of reported DNA matches between a suspect and genetic material recovered from a crime scene is usually represented at trial by the random match probability (RMP). The RMP identifies the DNA profile frequency in a reference population. This paper shows that RMPs contribute little to an assessment of the diagnostic significance of a reported DNA match beyond that given by the false positive laboratory error rate when RMPs are several orders of magnitude smaller than this error rate. Evidence that this principle is poorly understood by mock jurors is also presented, supporting the argument that introduction of RMPs may be prejudicial in some cases. A new approach, based on Bayesian principles and proficiency test data, is offered for identifying the diagnostic significance of DNA and other forensic science evidence.
Keywords: DNA, random match probability, Bayesian
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