Design and manufacture of surface textures on gun cartridge cases to trap DNA material

Abstract

US and Australian work has shown that the effectiveness of extracting deoxyribonucleic acid (DNA) from standard gun cartridges is low and so analysis costs are high ( www.cci.gov/Reference/LpDNACtg_files ). The presence of greater than 1 ng of trapped bio-material would increase the success rates of DNA profiling and facilitate cheaper DNA analysis. The aim of this work is to increase the amount of recoverable DNA from a gun user deposited on fired cartridges, using microtextured surfaces as DNA receptors. Success would increase the probability of identifying perpetrators of gun crime through DNA matching. Various textures have been applied to flat surfaces of cartridge case material and the effects of those surface textures on trapping skin materials have been evaluated. In addition to treated/patterned surfaces, standard emery abrasive paper was adopted as a control medium. From the different surfaces tested, the emery abrasive paper was found to be most effective at trapping skin debris. Rough surfaces with pyramid textures, which are similar to features on emery paper, were subsequently manufactured on cartridge rims by a standard knurling process. Scratch tests were carried out to simulate the process of handling and loading these cartridges during the use of firearms. DNA test results of the knurled cartridges after firing, showed a high success rate of DNA profiling and high matching percentage to the donor's DNA profile.