ISSN: 0022-1198
CODEN: JFSCA
Page Count: 10

Interpreting DNA Mixtures
Weir, BS
North Carolina State University, NC

Triggs, CM
University of Auckland,

Buckleton, J
ESR: Forensic, Mt. Albert Science Center, New Zealand

Walsh, KAJ
ESR: Forensic, Mt. Albert Science Center, New Zealand

Stowell, LI
ESR: Forensic, Mt. Albert Science Center, New Zealand

Starling, L
ESR: Forensic, Mt. Albert Science Center, New Zealand

(Received 2 January 1996; accepted 5 August 1996)

Abstract

The interpretation of mixed DNA stains is explained in the context of likelihood ratios. The probabilities for the mixed-stain profile are evaluated under alternative explanations that specify the numbers of contributors and the profiles of any known contributors. Interpretations based simply on the frequencies with which random members of a population would not be excluded from a mixed-stain profile do not make use of all the information, and may overstate the strength of the evidence against included people. The effects of the numbers of contributors depends on whether all the alleles at a locus are present in the mixed stain. A general equation is given to allow likelihood ratios to be calculated, and includes the “2p” modification suggested by the 1996 NRC report. This modification is not always conservative. A computer program to perform calculations is available.

Keywords:
forensic science, mixed stains, DNA profiles, likelihood ratios

Paper ID: JFS14100J
DOI: 10.1520/JFS14100J
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