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16 September 2014 Confirmatory analysis of field-presumptive GSR test sample using SEM/EDS
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Proceedings Volume 9236, Scanning Microscopies 2014; 92361C (2014)
Event: SPIE Scanning Microscopies, 2014, Monterey, California, United States
RedXDefense has developed an automated red-light/green-light field presumptive lead test using a sampling pad which can be subsequently processed in a Scanning Electron Microscope for GSR confirmation. The XCAT’s sampling card is used to acquire a sample from a suspect’s hands on the scene and give investigators an immediate presumptive as to the presence of lead possibly from primer residue. Positive results can be obtained after firing as little as one shot. The same sampling card can then be sent to a crime lab and processed on the SEM for GSR following ASTM E-1588-10 Standard Guide for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry, in the same manner as the existing tape lifts currently used in the field. Detection of GSR-characteristic particles (fused lead, barium, and antimony) as small as 0.8 microns (0.5 micron resolution) has been achieved using a JEOL JSM-6480LV SEM equipped with an Oxford Instruments INCA EDS system with a 50mm2 SDD detector, 350X magnification, in low-vacuum mode and in high vacuum mode after coating with carbon in a sputter coater. GSR particles remain stable on the sampling pad for a minimum of two months after chemical exposure (long term stability tests are in progress). The presumptive result provided by the XCAT yields immediate actionable intelligence to law enforcement to facilitate their investigation, without compromising the confirmatory test necessary to further support the investigation and legal case.
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Sarah J. Toal, Wayne D. Niemeyer, Sean Conte, Daniel D. Montgomery, and Gregory S. Erikson "Confirmatory analysis of field-presumptive GSR test sample using SEM/EDS", Proc. SPIE 9236, Scanning Microscopies 2014, 92361C (16 September 2014);

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