Advances in Analysis of Gunshot Residue

Analysis of gunshot residue (GSR), produced by the discharge of afirearm, can assist in the association of a suspect with a crime and in the recon-struction of the sequence of events preceding the crime. The golden standard inthe analysis of GSR is scanning electron microscope equipped with a detector forthe X-ray emission (SEM/EDX). SEM/EDX allows automatic detection of parti-cles containing heavy elements (such as GSR), imaging of particles detected andchemical analysis by EDX. Toxicological and environmental concerns led ammu-nition manufacturing towards products not containing Pb and other heavy metals.For SEM/EDX it is difficult to characterise the particles from lead-free ammunitionand particles from heavy metal free (HMF) cartridges are impossible to be automat-ically detected. Possible new alternatives could be electron backscattered diffractiondetectors (EBSD), ion beam analysis (IBA), time-of-flight secondary ion mass spec-trometry (ToF-SIMS), Raman chemical maps, attenuated total reflectance (ATR)imaging and FTIR spectroscopy or, to a lesser extent due to lack of imaging capabil-ities, chromatography and mass spectrometry. The evaluation of the time since thelast discharge is another interesting forensic problem associated to GSR, needingfurther research for routine application in casework.