2018
Angus Newton
Charleston, WV
Firearms examiners are frequently asked to provide an estimate on the distance between the muzzle of the firearm suspected to have been used and the target surface, at the time the shot was fired. To achieve this, the firearm residue pattern around the bullet entry hole is examined and compared with examples prepared at various distances using the same firearm and ammunition combination. Difficulties in providing estimates can occur when circumstances have meant changes to the residue pattern might have happened between the time of the shot being fired and the laboratory examination taking place. Changes in the residue pattern might be expected to occur if the victim has moved or bled significantly after the incident, or if the victim has died outside and significant rainfall has occurred before investigators can protect the scene environment. Uncertainties exist around the amount of change that might be expected and there is currently minimal research to provide information to support the examiner’s interpretation. This talk will present the results of a recently completed research project that aimed to fill the knowledge gap around the persistence of propellant particles on different surfaces after being subjected to different influencing factors. Two different commonly encountered calibers were chosen (.22LR and 9mm Luger) and fired from pistols to provide caseworkers with research examples from which to draw upon. Different propellant types within each caliber were also selected to study the influence of different morphologies on the persistence. Potentially influencing factors such as movement, bleeding and precipitation were studied in the research.