Evaluation of soaking to recover trace DNA from fired cartridge cases

ABSTRACT

The recovery of trace DNA from cartridge cases is of common interest across many jurisdictions. Soaking offers improved profiling success rates over traditional methods. We evaluated the effects of firing, calibre, and metal composition on controlled and handled DNA samples utilizing a soaking method. Our results show that firing decreases the quantities of DNA recoverable from cartridge cases and higher quantities of DNA are recoverable from nickel ammunition compared to brass. In spiked samples, calibre of ammunition had no significant effect on DNA recovery. Despite slight to moderate DNA degradation and variable profiling success rates, spiked unfired and fired nickel cartridges resulted in more usable profiles than brass cartridges. These findings can aid in triaging the types of ammunition subjected to DNA testing.

KEYWORDS:

• Trace DNA
• cartridge case
• ammunition
• soaking

Acknowledgments

This research project was financially supported by the NSW Police Force and an Australian Government Research Training Program scholarship. In-kind support was provided by NSW Health Pathology, Forensic & Analytical Science Service. The authors would also like to thank the NSWPF Forensic Ballistic Investigation section for their assistance and support with the experimental work for this project, and Professor James Brown for his advice on statistical analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).