Characterisation of gunshot residue particles using self-consistent ion beam analysis

Individual particles of gunshot residue were studied with particle-induced X-ray emission and backscattering spectrometry using a 2.5 MeV H+ beam focussed to ∼4 μm and self-consistent fitting of the data. The geometry of these spherical particles was considered in order to accurately fit the corresponding particle spectrum and therefore to quantify the trace element composition of these particles. The demonstrable self-consistency of this method allows the compositions of most residue particles to be determined unambiguously and with a higher sensitivity to trace elements than conventional methods.