Quantification of cellular material on fired and unfired ammunition

In recent years, much attention has turned to the analysis of “touch” DNA on fired cartridge cases. This is typically due to the combination of limited physical evidence present in gun crimes and increased sensitivity of current methods in DNA analysis. Past research in this area has focused on assessing the post-collection DNA typing results; however, this study aims to quantify the number of epithelial cells or cell-free DNA that are present on cartridge cases throughout the handling process. This includes ammunition collected directly “out-of-box”, ammunition loaded into the magazine but not fired, and cartridge cases collected post-firing, as well as an examination of the impact that different manufacturers may have on the initial deposition of biological material. Cartridge cases from three manufacturers (Remington, Winchester and Federal) were collected at different points: Out-of-box prior to handling, following loading into a magazine, and post-firing. Subsequently the cartridge cases were stained using Diamond Dye, a nucleic acid binding dye. The observed data showed that cells/cell-free DNA was found on 93% of the “out-of-box” rounds, where Federal ammunition had a statistically significant number of cells/cell-free DNA fragments detected; also observed were cells/cell-free DNA on the post-loading and post-firing cartridge cases with an average of 551±172 and 130±75, respectively. Results indicate that, regardless of the collection point, cartridge cases are likely to have ample cellular material to produce interpretable DNA profiles.