Raman spectroscopy analysis and chemometric study of organic gunshot residues originating from two types of ammunition.

The detection and analysis of gunshot residues expelled during the discharge of the weapon play a potential role in criminal investigations. In this work, organic gunshot residues produced by using automatic rifle Kalashnikov caliber: 7.62×39mm and semi-automatic pistol Makarov caliber: 9×18mm were studied using Raman spectrometry. Samples of gunshot residues were collected from tissues placed on the targets at various distances in the range of 0-100cm. A distance of 20cm was chosen for organic particles collection. The comparison between the spectra of gunshot particles and those of nitrocellulose and stabilizers samples indicates that it is possible to use Raman spectroscopy for organic GSR analysis, which makes possible the distinction of calibers containing propellants with diphenylamine and those with ethyl centralite as stabilizers. Principal component analysis and support vector machine method applied to the Raman spectral data ranging from 1800 to 800cm-1 allow a differentiation between the two sets of spectra.