Distribution of gunshot residues--the influence of weapon type

Gunshot residue (GSR) analysis is a frequently used forensic method for investigating shooting events. In this process, GSR-particles are detected on pertinent objects, often the hands of a suspect, with energy dispersive X-ray microanalysis in a scanning electron microscope. The question asked in court is usually the following: "… has or has not a given shot been fired by the suspect (at a certain place and time)?" Unfortunately, this question frequently cannot be answered by the analyst. Only the presence or absence of "characteristic" GSR-particles on the investigated sample can be stated with confidence. All other assumptions are inherently biased by many factors that are usually only known by the culprit or are generally unknown. In order to draw more profound conclusions from GSR analytical results, the dynamics of GSR particles have to be considered, i.e., how these particles reach a suspect. Consequently, the formation of the plume after firing was investigated for eleven different firearms with high speed-video analysis. The results show that a vast scope exists between revolvers - distributing many particles near the shooter - and e.g. shotguns that are quite sealed. These differences between the various weapon types should be considered for interpretation of the results of GSR-analysis.