Combined DNA Typing and Protein Identification from Unfired Brass Cartridges

Biological evidence analysis from contact traces is adversely affected by low quantity and quality of DNA. Proteins in thesesamples contain potentially individualizing information and may be particularly important for difficult surfaces such as brass, where DNA mayyield incomplete profiles. In this study, touched unfired brass cartridges were sampled using dry tape or wet swabs and analyzed by separatingDNA and protein from the same collected material, thus producing both genomic and proteomic information. DNA recovery was similar forboth collection methods, with tape yielding an average of 1.36+-1.87 ng and swabs, 1.34+-3.04 ng. Analysis by mass spectrometry identi-fied 95 proteins, with the two collection methods showing no significant difference (p=0.76) in the average number of collected proteins:44.+-10.9, (tape) versus 47.9+-0.4 (swabs). Proteins can be collected from fingerprints at levels necessary to provide identifying informa-tion, thus expanding information obtained from challenging evidence.