Proportion of total DNA consistent with the known owner on different areas of law enforcement owned firearms

Abstract

If a DNA profile obtained from evidence is consistent with an individual, there are several hypotheses on the activity level that could be evaluated in relation to the evidence. Was the DNA deposited by the owner or routine handler of the firearm? Was the individual’s DNA transferred via another means to the firearm? Gaining insights as to the quantities of DNA typically obtained from an owner of a firearm from different areas of the item may aid the examiner in more effectively evaluating the evidence. This study focused on deoxyribonucleic acid (DNA) collected from the trigger and trigger guard, the frame and slide, and the front and rear sight areas of 16 law enforcement-issued firearms. All samples that were suitable for comparison supported the DNA profile under the proposition if the owner of the firearm was a contributor to the DNA profile obtained from the sample. Additionally, 93% of the samples were assigned a likelihood ratio (LR) associated with a contributor that was estimated to account for greater than 70% of the DNA profile. Establishing data that can be used for evaluative reporting will enhance the DNA examiner’s ability to better explain the evidence in a courtroom setting.