GSR particles and their evidential value

Analysis of gunshot residues (GSR) is one of major areas in microparticle investigation. Results of the analysis usually have a high evidential value, but some information about potential secondary contamination by GSR is needed to maintain its value. A three-year study was carried out for ascertaining the level of possible secondary contamination monitoring GSR particles in urban means of transports in Prague (underground, trams, busses), taxi cars, randomly chosen civil vehicles, vehicles and trains of suburban transport, at places with a high concentration of people (supermarkets, hypermarkets, banks and financial institutions, premises of post offices). We also performed sampling at premises of the Institute of Criminalistics Prague (common areas, corridors, laboratory rooms), at police stations and in patrol cars of the Police of the Czech Republic, including Prague Metropolitan Police. Next, persons form selected professional groups of inhabitants (policemen, car mechanics, civilians without contact with a firearm and people who are in contact with hunting weapons - huntsmen and gamekeepers) were sampled as well.