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LIBS as an Emerging Method for the Detection of Firearm Discharge Residues
Thursday, March 11, 2021: 9:05 AM - 9:40 AM
Speaker(s)
Description
Newer computational and technological advances are opening opportunities for alternative approaches to identify and interpret gunshot residues (GSR). This study illustrates the versatility of Laser-Induced Breakdown Spectroscopy (LIBS) to identify traces produced when a firearm is discharged, providing crucial information, such as links to a person of interest, the direction of a bullet entering a particular target, and the muzzle-to-target shooting distance. First, a LIBS method was developed as a rapid screening for the identification of GSR from the hands of individuals. The method's validation was conducted using a tailor-made microparticle standard and authentic samples collected from the hands of over 600 shooters and non-shooters. This novel approach's performance was cross-validated with multiple techniques such as SEM-EDS, electrochemistry, and LA-ICP-MS, with accuracy superior to 95% when using machine learning classification methods. Second, LIBS's feasibility to identify GSR around bullet orifices was evaluated in complex substrates that are often difficult to remove from the crime scene. LIBS successfully identified the GSR traces from 21 glass, wood, and drywall pieces shot from close range. Finally, 98 fabrics of different colors, patterns, and conditions were shot using pistols and revolvers with various ammunition. Spatial distributions of IGSR were used to estimate the shooting range. Unlike the conventional color assays, LIBS produced permanent chemical images that allow objective statistical analysis. Principal Component Analysis and Discriminant Analysis resulted in 100% correct classification of the shooting ranges, while color tests resulted in 58.5% correct classification. This study demonstrates that LIBS provides a robust novel alternative for screening various materials relevant to shooting events, affording rapid examination of traces, and informed decision-making during the investigation.
Additional Info
Keywords: Please select up to 4 keywords ONLY:
Laser,Neural Network,Reference Material,Trace Analysis,Spectroscopy
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