Since the standard practice for gunshot residue (GSR) analysis, SEM-EDS, is time-consuming and based on categorical classification models without considering case circumstances, the goal of the current research was to develop standard materials and alternative methods for characterizing and interpreting inorganic gunshot residue (IGSR).
This research project developed primer GSR (pGSR) standards from 60 discharged primers that were fully characterized by three techniques. The number of GSR particles, their composition, and elemental concentrations demonstrated stability for over a year, providing a resource to be used as a ground for future studies. The standards showed some elemental profiles not yet reported in the literature. A survey of low- and high-risk background populations and various samples from control-shooters was obtained from the hands of 975 individuals. Samples were analyzed by SEM-EDS and by a fast screening test (LIBS). Machine learning methods were applied for predictive classification with accuracies better than 90 percent. In addition, a probabilistic assessment of the evidential value of GSR was evaluated. Overall, this research provides updated information about IGSR and a comprehensive assessment of current and novel analytical and interpretation methods. Data produced is anticipated to provide the forensic community with greater knowledge and improved tools for more definitive conclusions. 14 figures, 9 tables, and 62 references