Estimating the number of contributors to a DNA profile
Thorne Egeland1 , Ingvild Dalen2 and Petter F. Mostad3

(1) Biostatistics, Rikshospitalet University Hospital, 0027 Oslo, Norway
(2) University of Oslo, Oslo, Norway
(3) Chalmers Technical University, Göteborg, Sweden


Thorne Egeland
Email: thore.egeland@basalmed.uio.no
Phone: +47-228-51148
Fax: +47-228-51313

Received: 20 December 2002 Accepted: 25 April 2003 Published online: 14 August 2003

Abstract The broad topic of this paper is the evaluation of DNA evidence in criminal cases. More specifically, we deal with mixture evidence which refers to cases where there are, or could be, several contributors to a biological stain based on, e.g., blood or semen. The present paper adresses DNA mixtures based on single nucleotide polymorphism (SNP) markers, i.e., diallelic markers. Based on STR analysis, it is in most cases easy to identify the presence of a mixture since three or four bands will show up with a high probability for at least one locus. Obviously, this will not be the case for diallelic markers and interpreting mixtures will be a great challenge. We address this problem by first approaching the more general problem of estimating the number of contributors to a stain. In addition we discuss how the markers should be selected and how many are required