Potential for DNA loss during collection and packaging of fired cartridge cases at a crime scene

DNA recovery from fired cartridge cases (FCCs) found at a crime scene is complicated by the limited DNA amounts typically available for collection. While this challenge is unavoidable, recovery rates may be improved by optimizing handling and packaging processes to better preserve the available DNA. Here we compared existing methods of collecting and packaging FCCs at a crime scene and assessed the utility of a novel cartridge collection device to determine which combination best preserves DNA integrity and amounts. FCCs loaded with touch DNA or blood and some DNA-free FCCs were collected and placed into paper or plastic packaging by one of 12 methods. Packages were handled in a manner that mimicked handling during casework, after which the location of DNA within the packaging was assessed to determine where transfer/loss had occurred. We observed that DNA can be lost from FCCs to an examiner's glove during collection, to the inside of packaging after handling and transport, and between FCCs in the same packaging. The novel cartridge collection device mitigated this transfer in many cases and could be considered a means of preserving DNA on FCCs. The results demonstrate the potential for preserving DNA by avoiding direct contact between the FCC and other items.