Ammunition Identification by Means of the Organic Analysis of Gunshot Residues Using Raman Spectroscopy

Abstract

The ability to unequivocally identify a gunshot residue (GSR) when a firearm is discharged is a very important and crucial part of crime scene investigation. To date, the great majority of the analyses have focused on the inorganic components of GSR, but the introduction of "lead-free" or "nontoxic" ammunitions makes it difficult to prevent false negatives. This study introduces a fast methodology for the organic analysis of GSR using Raman spectroscopy. Six different types of ammunition were fired at short distances into cloth targets, and the Raman spectra produced by the GSR were measured and compared with the spectra from the unfired gunpowder ammunition. The GSR spectrum shows high similarity to the spectrum of the unfired ammunition, allowing the GSR to be traced to the ammunition used. Additionally, other substances that might be found on the victim's, shooter's, or suspect's clothes and might be confused with GSR, such as sand, dried blood, or black ink from a common ballpoint pen, were analyzed to test the screening capability of the Raman technique. The results obtained evidenced that Raman spectroscopy is a useful screening tool when fast analysis is desired and that little sample preparation is required for the analysis of GSR evidence.

Tiro-aztarnen identifikazioa, auzitegi-laborategien erronka

“…Hasiera batean Raman espektroskopia tiro-aztarnetako konposatu ez-organikoen identifikaziorako erabili zen, berun eta bario gatzen identifikaziorako hain zuzen ere [38]. Azkeneko urteotan, teknika horrek konposatu organikoen identifikazioa ahalbidetu du [39]. Metodologia estatistikoekin batera, espektroskopia hau munizioaren kalibrea ezagutzeko ere erabili da [40].…”

Fast Detection and Chemical Characterization of Gunshot Residues by CMV-GC-MS and LIBS

“…For this reason, a spherical morphology alone is not an indication of GSR particles [Grima et al, 2012]. Particle size can range between 0.1-100 µm, but most are found to be less than 10 µm [Flynn et al, 1998;López-López et al, 2012;Moran et al, 2013].…”

“…The target elements (Ba, Pb, and Sb) can be found together in the form of spherical particles that are a few microns in diameter (0.1-100 µm) [Flynn et al, 1998;López-López et al, 2012].…”

“…Disadvantages of color tests include high rate of false positive results as a result of positive reactions with other substances, and are dependent on each individual visual color perception [Silva et al, 2009;Vanini et al, 2014]. In addition, color tests react to the presence of target elements but cannot be used as a confirmation of GSR presence López-López et al, 2012]. Therefore, elemental analysis is more reliable and is necessary to confirm the presence of target elements in GSR samples.…”

“…Chromophoric tests that detect the presence of nitrites and nitrates are unreliable because there are multiple materials found to contain these functional groups, such as fertilizers [Hilton et al, 2010]. These color tests react to the presence of functional groups but cannot be used as a confirmation of GSR presence López-López et al, 2012]. Therefore, organic analysis is more reliable and is necessary to confirm the presence of target organic compounds in GSR [Burleson et al, 2009;Silva et al, 2009;Weyermann et al, 2009;Zeichner et al, 2009;Brożec-Mucha et al, 2011;Arndt et al 2012].…”