Trajectory reconstruction from trace evidence on spent bullets II. Are tissue deposits eliminated by subsequent impacts?

STR-based individualisation of biological deposits on bullets after perfora tion of tissue, can identify the person injured or killed by a particular b ullet and comparison with the firearms used can identify the weapon and thu s possibly the person who did the shooting. In this study, the effect of su bsequent impacts on intermediate targets such as loss of cells was investig ated by amplification of mitochondrial (mt) DNA. Bovine tissue was perforat ed and the 9 mm Luger FMJ bullets were recovered from the bullet collector. The mt cytochrome-b (cyt-b) gene could be amplified by the polymerase chai n reaction (PCR) from 14 out of 15 bullets. Examination with a scanning ele ctron microscope (SEM) and an energy-dispersive X-ray spectrometer (EDS) de monstrated the presence of minute dried tissue deposits on all bullets (n = 10) but was not able to establish preferential locations. In a series of 2 5 gunshots, various intermediate targets (glass, wood, car metal, gypsum bo ard, asphalt) were perforated/impacted following perforation of tissue and the cyt-b gene could be typed from all bullets. It is concluded that subseq uent impacts on intermediate targets do not eliminate enough biological dep osits to render DNA analysis impossible and that the amplification of mtDNA is a useful additional method.