Exploratory analysis of gunshot residue by SEM-EDX and chemometrics for firearm discrimination: a proof-of-concept approach

Gunshot residue (GSR) analysis is a critical component in the forensic investigation of shooting incidents. It offers valuable evidentiary insights and contributes to the reconstruction of crime scenes. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDX) is widely recognized as a principal analytical technique for GSR characterization due to its high selectivity and specificity for inorganic particles. Herein we present the application of SEM-EDX supported by chemometric techniques for the classification of GSR samples according to firearm calibre under controlled experimental conditions. Elemental concentration data obtained from GSR particles were analysed using statistical models, including k-Nearest Neighbours classification and Random Forest Classification, to achieve effective discrimination. The proposed proof-of-concept approach demonstrates a time-efficient, non-destructive, and exploratory methodology for GSR analysis. The findings indicate methodological feasibility offering substantial implications for forensic firearm identification and highlight the need for broader validation across diverse firearm–ammunition combinations and substrates.