Enhanced GSR Detection By Multispectral Illumination for Forensic Shooting Distance Analysis

In forensic science, measuring the shooting distance is crucial for reconstructing crime scenes involving firearms. This paper evaluates the use of multispectral imaging in the infrared range to enhance the detection and analysis of gunshot residue (GSR) particles on fabric. We analyzed eight white cotton samples shot from distances ranging from 5 to 50 cm. To define the best wavelength, we selected the one where the particles in the image were most contrasted against the fabric, a factor heavily dependent on the color of the fabric. Then, Principal Component Analysis (PCA) is applied to multispectral images, at the selected best wavelength, to obtain high-contrast images that significantly improve GSR detection. The polar coordinate transformation aligned the particle analysis with the radial distribution of residues, optimizing the detection process. Our findings indicate that multispectral imaging, especially when combined with advanced image processing techniques, offers a non-invasive measurement method for forensic analysis, providing reliable data that can complement traditional methods