Journal de recherche médico-légale

Yield of Male Contact DNA Evidence in an Assault Simulation Model

Abstract

Michael P Sandoval, William M Green, Edward A Panacek, Edward A Panacek and Sree Kanthaswamy

The conditions under which contact DNA analysis yields useful recovery of materials is not well known. Using simulated models of grabbing and struggling, the recovery of male contact DNA transferred from male “assailants” to female “victims” was investigated. The upper and lower arm areas of female subjects (sites for the modeled assaults) were swabbed for male DNA. Extracted DNA was quantified using the Quantifiler® Duo DNA Quantification kit and amplified using the AmpFlSTR® Identifiler® and the AmpFlSTR® YfilerTM PCR Amplification kits. The qPCR quantification results detected male “assailant” DNA from the female “victims”. However, no viable male profiles were obtained when the DNA was subjected to short tandem repeat (STR) analysis with the Identifiler® and Yfiler™ kits. The grab and struggle scenarios yielded up to 20 pg/μL and 40 pg/μL of male contact DNA from female subjects, respectively, DNA amounts which are below the detection threshold of most commercial human STR identification kits. Although contact DNA levels are highly variable, this study showed that the likelihood of DNA deposition on skin from assailant to victim was substantially greater when a struggle ensues. The results of the present study are limited by small sample size, but imply that further research for improving recovery and amplification techniques of contact DNA should be sought to increase the probative value of this evidence in sexual assault investigations.