Overall Proportion of Total DNA Consistent with an Individual Briefly Handling a Firearm

Abstract

In forensic investigations, DNA profiles are routinely obtained from firearms evidence and alternative hypotheses may be proposed for consideration on the activity level. DNA profiles found to be consistent with the DNA profile of a specific individual could be a result of directly handling the firearm or other modes of transfer of DNA. Sixteen law-enforcement-owned firearms were evaluated with samples collected from the frame and slide area, the trigger and trigger guard area, and the front and rear sights after brief handling by laboratory personnel. Twenty-two out of forty-eight samples resulted in DNA profiles suitable for comparison, of which six resulted in likelihood ratios (LR) that demonstrated support for the hypothesis that included the brief handler as a contributor to the DNA profile obtained from the sample. Five of these samples were obtained from the frame and slide and one was from the trigger and trigger guard area. None of the DNA profiles obtained from the sights supported the inclusion of the brief handler as a contributor to the DNA profile. Gaining knowledge and supporting data on the nature of DNA profiles typically obtained from both owners and brief handlers can be useful for the purposes of evaluative reporting when considering results obtained from firearm evidence.