Specific traces in stun gun deployment

Abstract

Stun guns are electric shocking devices that can be deployed as defensive or offensive weapons. The aim of this study was the identification of several types of trace evidence for corroborating deployment and providing clues to the weapon actually used. In a series of some 250 tests, the after-effects of firing a stun gun were studied under the differential influence of factors, such as time duration, distance from target, and bare skin vs clothing as target surface. Examination with scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) demonstrated the presence of metallic deposits corresponding to the electrodes of the device used. The observed differences in the number of these pellets were related to the length of deployment in seconds and to the distance of the weapon from the target surface. Longer duration of firing was consistently associated with a larger number of metallic deposits. Elemental composition of the latter provided clues to the type of device used and its current status in terms of wear and tear. Further trace evidence we examined included craters on the target surface and their pattern of dissemination on human skin, textiles, and leather. It is concluded that the use of carbon tabs for examination with SEM/EDS offers a practicable method for collecting trace material following stun gun deployment. Important groups of trace evidence do exist, and their collection and examination appear feasible.