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Application of Random Match Probability Calculations to Mixed STR Profiles

NCJ Number
246065
Journal
Journal of Forensic Sciences Volume: 58 Issue: 2 Dated: March 2013 Pages: 474-485
Author(s)
Todd Bille, M.Sc.; Jo-Anne Bright, M.Sc.; John Buckleton, Ph.D.
Date Published
March 2013
Length
12 pages
Annotation

This article compares the advantages and disadvantages of the CPI and LR methods to the RMP method.

Abstract

Mixed DNA profiles are being encountered more frequently as laboratories analyze increasing amounts of touch evidence. If it is determined that an individual could be a possible contributor to the mixture, it is necessary to perform a statistical analysis to allow an assignment of weight to the evidence. Currently, the combined probability of inclusion (CPI) and the likelihood ratio (LR) are the most commonly used methods to perform the statistical analysis. A third method, random match probability (RMP), is available. This article compares the advantages and disadvantages of the CPI and LR methods to the RMP method. The reseachers demonstrate that although the LR method is still considered the most powerful of the binary methods, the RMP and LR methods make similar use of the observed data such as peak height, assumed number of contributors, and known contributors where the CPI calculation tends to waste information and be less informative. Abstract published by arrangement with John Wiley & Sons.