Noninvasive, visual examination for the presence of gunshot residue on human skin

Abstract

When a firearm is discharged, the highest concentration of gunshot residue (GSR) is located on a shooter's hands, forearms, and clothing. Currently, collecting GSR from an individual's hands is accomplished with a carbon disk that is submitted for confirmatory analysis in a forensic laboratory. Presumptive chemical tests can be performed in the field, but these tests consume a portion of the GSR particles leaving a reduced amount of evidence available to be collected and sent to a forensic laboratory. An abundance of research exists for detecting GSR particles instantly on different fabrics using an alternate light source (ALS). This study expanded on that research and developed a noninvasive, visual examination to detect GSR on a suspected shooter's hands without destroying or removing any particles prior to collection. The hands of individuals who recently discharged a firearm were examined under a light source between 475 and 530 nm and an infrared (IR) camera. The fluorescent particles observed on a shooter's hands under 520 nm were similar in size and appearance to GSR particles observed on fabrics under an ALS. The fluorescent particles were collected and analyzed for GSR, and the results indicated that GSR particles were present. More testing needs to be conducted to determine if the fluorescent particles observed are inorganic or organic GSR particles. There is also potential to detect GSR under IR light; however, more research needs to be conducted to determine the composition of the particles observed after image enhancement.

Innovative Vibrational Spectroscopy Research for Forensic Application

“…In 2022, Husak presented a noninvasive methodology to detect GSR on human skin. 70 The study utilized alternate light sources (ALSs) and an IR camera. A total of 101 shooters' hands were photographed immediately after firing under visible and ALSs.…”

“…In 2022, Husak presented a noninvasive methodology to detect GSR on human skin . The study utilized alternate light sources (ALSs) and an IR camera.…”

Interpol Review of Gunshot Residue 2019 to 2021

“…Husak examined in Ref. [ 29 ] whether an alternate light source could help collect gunshot residue on the hands of shooters, this by visualising fluorescent particles. For this study, about 100 police officers were involved in the sampling, firing a Glock 9 mm or a 0.40 calibre with American Eagle ammunition.…”

Crime Light Imaging (CLI): A Novel Sensor for Stand-Off Detection and Localization of Forensic Traces

“…Due to a large variability of possible latent traces and substrates on crime scenes, the ALSs should include a set of illumination sources from the UV to NIR spectral range in order to cover, for example, the detection of untreated or treated fingerprints [ 15 , 16 , 17 ], fibers [ 18 , 19 ], blood [ 20 ], body excretions [ 21 , 22 , 23 , 24 ], drugs [ 25 ], bruises [ 26 ], gunshot residues [ 27 , 28 , 29 ], bones [ 30 , 31 ] and papers and inks [ 28 , 32 , 33 ]. By combining a proper illumination source and wavelength filtering of the signal in front of a photo camera, the capability to detect latent traces on a larger number of substrates can be achieved [ 12 , 24 ].…”