Firearms, particularly handguns, are frequently used in violent crimes, and thus, spent cartridge casings may be recovered from shooting scenes. Casings have the potential to harbor DNA deposited by the loader of a weapon, which can be used to produce genetic profiles. While short tandem repeat (STR) analysis is the standard method of DNA identification in forensic science today, many researchers have reported limited success obtaining these data from spent casings. The primary goal of this study was to examine if it is possible to generate mitochondrial DNA (mtDNA) profiles from spent cartridge casings. Volunteers loaded cartridges into the magazine of a handgun, the cartridges were fired, and casings were collected and swabbed. DNAs were extracted, mtDNAs were amplified and sequenced, and haplotypes were generated. Two swabbing methods, individual and cumulative, were compared to determine which was most likely to result in mtDNA haplotypes consistent with the loader. Cumulatively swabbing resulted in a greater frequency of consistent haplotypes, as well as a lower mixture frequency than individually swabbing. Furthermore, a larger amount of the first loaded/last fired cartridge casings compared to the first fired cartridges exhibited contamination. Consensus haplotypes, which contained shared polymorphisms from multiple swabs, yielded a greater percentage of consistent haplotypes than the individually swabbed spent casings, but did not outperform cumulatively swabbing. However, none of these differences were statistically significant. Ultimately, mtDNA analysis is a reliable method to generate genetic profiles recovered from spent cartridge casings.
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