The importance of male underwear in cases of alleged sexual assault

Abstract

The potential evidential value of male underwear in cases of alleged sexual assault is often overlooked. Male underwear can be a critical item in the investigation of alleged sexual assaults. Body fluids/DNA, which may transfer to the penis during sexual contact, may in turn transfer to the inside front of the underwear, and persist for months or years, provided the underwear are not washed. Here, we demonstrate how the case circumstances drive the sampling strategy of male underwear, in order to maximize the effectiveness of the forensic analysis. Sampling considerations including recovery methods and sampling sequence are discussed, and a methodical examination strategy of male underwear is proposed. To highlight the pertinence of male underwear to the investigation of alleged sexual assaults, three real-life cases are discussed, in which male underwear were examined for multiple body fluids/DNA, and the findings obtained proved evidentially significant. The different cases demonstrate the versatility of male underwear examination in situations, where different body fluids and DNA may transfer based on the specific allegation, and emphasize how targeted sampling can allow the scientist to assess the probability of the findings based on two competing propositions. Accurate sampling strategies are imperative for robust probability assignment in evaluative reporting of scientific findings.