Estimating the Number of Contributors to Forensic DNA Mixtures: Does Maximum Likelihood Perform Better Than Maximum Allele Count?

• NCJ Number: 233653
• Journal: Journal of Forensic Sciences Volume: 56 Issue: 1 Dated: January 2011 Pages: 23-28
• Author(s): Hinda Haned, M.S.; Laurent Pene, M.S.; Jean R. Lobry, Ph.D.; Anne B.. Dufour, Ph.D.; Dominique Pontier, Ph.D.
• Date Published: January 2011
• Length: 6 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This paper examines the number of contributors to forensic DNA mixtures.

Abstract

Determining the number of contributors to a forensic DNA mixture using maximum allele count is a common practice in many forensic laboratories. In this paper, the authors compare this method to a maximum likelihood estimator previously proposed by Egeland et al., that they extend to the cases of multiallelic loci and population subdivision. The study compared both methods' efficiency for identifying mixtures of two to five individuals in the case of uncertainty about the population allele frequencies and partial profiles. The proportion of correctly resolved mixtures was greater than 90 percent for both estimators for two- and three-person mixtures, while likelihood maximization yielded success rates 2- to 15-fold higher for four- and five-person mixtures. Comparable results were obtained in the cases of uncertain allele frequencies and partial profiles. Results support the use of the maximum likelihood estimator to report the number of contributors when dealing with complex DNA mixtures. (Published Abstract) Tables, figures, and references