ABSTRACT This study examines the relative success rates of DNA recovery from firearm locations normally handled during the process of loading and discharging the firearm, ejected cartridge cases, and unspent cartridges to aid in the association of the firearm, ammunition, or cartridge case to a potential perpetrator by means of DNA evidence. Four firearms were selected for study: a revolver, a pistol, a break-action shotgun and a pump-action shotgun. Thirty-seven percent (37%, 47/126) of the experimental samples from the exterior locations of the four firearms tested yielded DNA quantities suitable for further processing (≥ 240 pg), with an average yield of 1.1 ng of DNA per sample. DNA recovery was most successful from the grip of all four firearms (80% of trials) and the slide serrations of the pistol (87.5% of trials). An association between the shooter and the DNA profile obtained was established in 30% of the samples. The DNA profiles obtained were either of single source or mixtures from which the shooter could not be excluded as a contributor. In most cases, the shooter could not be excluded as the major contributor to the mixture; however, there were instances where the shooter could only be attributed to the mixture as a minor contributor of DNA. The remaining 70% of samples did not yield sufficient DNA or the profiles obtained were partial or complex mixtures. DNA recovery from samples taken from fired cartridge cases, unfired cartridges, and the top and sides of the magazine of a pistol were evaluated in a separate study. Only two of the 72 experimental samples, a sample from an ejected cartridge case and a sample from the magazine, yielded DNA quantities above the 240 pg amplification threshold. Only the magazine sample yielded a full 9 STR locus DNA profile that was attributable to the shooter. An additional experiment was conducted to examine the effects of heat, gases, and mechanical action on DNA recovery. Cellular material was deposited (via saliva) on the exterior of the ammunition loaded into the firearm. Samples from the cartridges cases discharged from the firearm and loaded unfired cartridges both demonstrated loss and degradation of DNA. DNA recovery from cartridges and ejected cartridge cases has extremely limited success, compounded by the act of discharging the firearm that compromises the quality of the DNA as a template for amplification.
[1]
Y Migron,et al.
Visualization of sebaceous fingerprints on fired cartridge cases: a laboratory study.
,
1998,
Journal of forensic sciences.
[2]
Mauro Pesaresi,et al.
Fingerprints as evidence for a genetic profile: morphological study on fingerprints and analysis of exogenous and individual factors affecting DNA typing.
,
2003,
Journal of forensic sciences.
[3]
R. V. Oorschot,et al.
DNA fingerprints from fingerprints
,
1997,
Nature.
[4]
Hiromitsu Kobayashi,et al.
Unique morphology of the human eye
,
1997,
Nature.
[5]
Ray A Wickenheiser,et al.
Trace DNA: a review, discussion of theory, and application of the transfer of trace quantities of DNA through skin contact.
,
2002,
Journal of forensic sciences.
[6]
J K Brown,et al.
Post firing visualisation of fingerprint on spent cartridge cases.
,
1996,
Science & justice : journal of the Forensic Science Society.
[7]
M M Schulz,et al.
Archived or directly swabbed latent fingerprints as a DNA source for STR typing.
,
2002,
Forensic science international.
[8]
T Sitalaximi,et al.
Autosomal microsatellite profile of three socially diverse ethnic Tamil populations of India.
,
2003,
Journal of forensic sciences.
[9]
A Zamir,et al.
Fingerprints and DNA: STR typing of DNA extracted from adhesive tape after processing for fingerprints.
,
2000,
Journal of forensic sciences.
[10]
R. Frappier,et al.
Developmental validation of a real-time quantitative PCR assay for automated quantification of human DNA.
,
2003,
Journal of forensic sciences.