Analysis Gunshot Residue (GSR) – Reconstruction of Crime Scenes

Abstract

GSR particles from the surroundings of bullet hole have been characterized as a function of primer type and particle distribution. SEM images were used to verify size and shape of the GSR particles and EDS to verify the elemental composition in a single particle. The same specimens are further subjected toTime of Flight Secondary Ion Mass Spectrometry (ToF SIMS) with a view to identify the respective surface chemistry, molecular nature and molecular mass of the GSR particles. Both inorganic and organic components of GSR in the elemental and combined form can be identified using SIMS.Secondary ion mass spectrum and the image analysis are carried out for selected particles. The mass peaks of oxides of lead, barium and antimony apart from the elemental masses are found. The combination of Pb/Ba/Sb and their oxides in a particular particle specifically establish the characteristics of a typical GSR particle. Molecular imaging and the distribution of the components in the GSR particle before and after sputtering are studied. Lead and its oxide are more concentrated in the surface of the particle compared to Ba and Sb. It is evident that SIMS can detect whether the components are either in the elemental or a compound form or a combination of both. The results of ToF SIMS clearly establish the feasibility of utilizing ToF SIMS as a tool for direct characterization of GSR from environmental polluted particles of the same nature for forensic applications.