On the prevalence of gunshot residue in selected populations - An empirical study performed with SEM-EDX analysis

摘要

The study was designed to obtain a comprehensive view on the prevalence of gunshot residue and the factors influencing their dispersion. 273 specimens collected from people of various professions, representing both users and non-users of firearms, as well as from the interior of a forensic laboratory were examined for the presence of gunshot residue. In specimens taken from hands of 100 people declaring no contact with firearms only one spherical particle containing lead, antimony and barium was found. Numbers of particles found in specimens collected from hands of 50 shooters varied from zero to numbers greater than 100 and were strongly correlated with the time interval between last shooting and collecting specimens. Within the first 4 h after shooting particles are being lost from the shooter's hands, and so transferred from shooters to their environment. Thus, the relatives of five hunters were examined during both the close and open hunting seasons to trace the potential secondary transfer in practice. Using the criterion of low risk of contamination with gunshot residue, i.e. 5 h after last handling a gun, only few specimens were encountered among these collected from hands of firearm users that contained characteristic particles and these occurred in small numbers. Frequent shooters, e.g. shooting instructors or firearm examiners, formed a class for themselves of high risk of contamination with gunshot residue. As a result of continuous monitoring of the laboratory (55 specimens examined so far), where the examinations of gunshot residue are being carried out, it has been proved that the laboratory is free from contamination and so confirmed the usefulness of protocols worked out. The obtained information provided empirical bases to the minimisation of the risk of contamination of the evidence as well as for the evaluation of the analytical findings in the expertise on gunshot incidents.