On the effect of shooting distance, ballistic model construction, doping and weapon type on the simultaneous analysis of DNA and RNA from backspatter recovered from inside surfaces of firearms

Abstract

Investigations at crime scenes after criminal acts involving gunshot injuries have occurred often encompass the analysis of traces of blood and so-called backspatter. Molecular genetic analysis of backspatter generated by contact shots and shots from very short distances has already been demonstrated to critically contribute to victim identification and the reconstruction of firearm-related crimes. Herein, we investigated the effect of several combinations of shooting distances and types of firearms on backspatter generation and co-extraction and simultaneous analysis of DNA and RNA isolated from traces of backspatter. Additionally, we assessed whether "triple contrast" doping of ballistic models interferes with forensic analysis of DNA, mtDNA and co-extracted mRNA and miRNA from backspatter collected from inside parts of firearms generated by experimental shootings. We show the effect of shooting distance and the type of firearm in experimental shootings on the yields of DNA and RNA co-extracted from backspatter and the success rates of forensic DNA profiling and RNA based organ identification. Furthermore, we demonstrate that "triple contrast" stained biological samples collected from inside surfaces of firearms are amenable to forensic DNA profiling and permit analysis of the entire mtDNA D-loop even for "low template" DNA amounts that preclude standard short tandem repeat DNA analysis.

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

“…With the prevalence of firearms throughout the world combined with the fact that firearms are inherently weapons, it is no surprise that firearms of all types are often submitted as evidence for DNA processing. As such, some research into the DNA collected from firearms and ammunition has already been conducted [3][4][5][6][7][8][9][10]. However, given the large quantities of firearms in the world, combined with their frequent association with crime, it is surprising that more research has not been published to date.…”