Investigation of the use of luminescent markers as gunshot residue indicators

- Conventional ammunition cartridges tagged with luminescent markers were shot.
- The luminescent particles detected under UV light improve evidence collection.
- Gunshot residues with marker and propellant compounds are identified by Raman spectroscopy.
- Unequivocal identification of GSR and marker can be achieved by SEM-EDX.

The addition of luminescent markers into ammunition cartridges is an appealing proposal to achieve a greater individual identification of the ammunition. The lanthanide elements present in these luminescent materials act as characteristic chemical markers that, also, offer the great benefit of making gunshot residues (GSR) collection easier. Although the use of luminescent markers offers numerous advantages, and can be a reliable future option in the cartridge ammunition market, little or nothing is known about the interaction of the marker with the ammunition compounds after the shot. For the forensic laboratories, it is of utmost importance to anticipate the commercialization of tagged luminescent ammunition by knowing the type of particles produced after the discharge. That is, to investigate if markers merge with GSR to form single particles or, on the contrary, they form individual particles that travel separately from the GSR particles. In this work, conventional ammunition cartridges tagged with two types of luminescent markers were shot. Then, the particles produced were visualized under UV light on the floor, clothing targets and the shooter. The luminescent particles spread over the floor determined the shooter position and the bullet trajectory. The illumination of the shot targets allows the visualization of the GSR patterns only using a portable UV lamp, avoiding the use of colorimetric test. The GSR particles were collected and subjected to SEM-EDX and Raman spectroscopy analysis to get information about their inorganic and organic composition. The results indicated that part of the marker and the GSR merge and travel together. With this, particles composed by the marker and propellant organic compounds can be identified by Raman spectroscopy, and the unequivocal identification of the GSR and the marker can be achieved by SEM-EDX. Consequently, the luminescent particles detected under UV light improve the evidence collection and offer information about the GSR and the marker. Additionally, this study support the use of luminescent ammunition to study, for example, the transfer or persistence of GSR.

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