**4.3. Differentiation of gunshot residues**

In a study performed using a VSC 2000 system to determine gunshot residues on dark clothing in 2006, as well as another study performed using a modified Griess test to determine gunshot residues on dark or multicolored clothing in 2006, researchers suggested that the use of IR or IR-enhanced photography may enhance the gunshot residue pattern [49, 50]. In a study performed in 2007 by Lin et al., gunshot residue was collected from dark cloth samples following firing from 15, 30 and 60 cm ranges using a 9-mm pistol (Smith & Wesson) with 9 mm bullets (NPA 01 3). Components that absorb the IR of gunshot residue were determined. The authors indicated that "the number of black particles observed using IR was approxi‐ mately 418, 317 and 63 within a 10 cm radius around the entrance hole when the firearm was discharged at distances of 15, 30 and 60 cm of shooting, respectively". Other features of this assay for the determination of distance shooting are that this test permits records and is not destructive for gunshot residue [48]. In another study, Patne et al. claimed that chemical imaging technology may be used to eliminate different brands of ammunition based on the fluorescence characteristics of the propellant grains on clothes without destroying the evidence before further analysis may be conducted [47]. Furthermore, Bueno et al. suggested the use of NIR-Raman microspectroscopy combined with advanced statistics to detect gunshot residues in 2012. Researchers claimed that NIR Raman microspectroscopy has the potential for reagentless differentiation of gunshot residues based on forensically relevant parameters, such as the calibre size, and this method should have a significant impact on the efficiency of crime scene investigations when fully developed [51].
