Standard Practice for Gunshot Residue Analysis by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectrometry
5.1 This document will be of use to forensic laboratory personnel who are involved in the analysis of GSR samples by SEM/EDS (5).
5.2 SEM/EDS analysis of GSR is a non-destructive method that provides (6, 7) both morphological information and the constituent elements detected in individual particles.
5.3 Particle analysis contrasts with bulk sample methods, such as atomic absorption spectrophotometry (AAS) (8), neutron activation analysis (NAA) (9), inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS), where the sampled material is dissolved or extracted prior to the determination of total element concentrations, thereby sacrificing size, shape, and individual particle identification.
1.1 This practice covers the analysis of gunshot residue (GSR) by scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS). The analysis is performed using automated software control of both the SEM and EDS systems, to screen the sample for candidate particles that could be associated with GSR. Manual control of the instrument is then used to perform confirmatory analysis and classification of the candidate particles. This practice refers solely to the analysis of electron microscopy stubs (1).2
1.2 Since software and hardware formats vary among commercial systems, guidelines will be offered in the most general terms possible. For proper terminology and operation, consult the SEM/EDS system manuals for each instrument.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard cannot replace knowledge, skills, or abilities acquired through education, training, and experience (Practice E2917), and is to be used in conjunction with professional judgment by individuals with such discipline-specific knowledge, skills, and abilities.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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