NCJ Number
77118
Date Published
1979
Length
59 pages
Annotation
This report describes a new and accurate method for the detection of gunshot residue (GSR) and the organization and content of workshops which taught the method to forensic scientists.
Abstract
The scanning electron microscope/energy dispersive X-ray analyzer (SEM/EDXRA) method, recently developed by the Aerospace Corporation with the support of LEAA, depends upon particle-by-particle analysis of GSR removed from the hands with sticky tape. GSR is composed of micrometer-sized particles which are physically characteristic of their mode of formation as well as chemically related to their source materials. Each of these particles can be visualized and sized with the SEM and analyzed for elements heavier than sodium with the EDXRA. The method was taught to 31 scientists from 28 laboratories in 5-day workshops in 1979. These workshops consisted of lectures, discussion, and laboratory sessions on GSR characteristics, on comparison of light and scanning electron microscopy, on theory of electron optics and SEM, and on practical instrumental details. Also included were the theory and practice of X-ray analysis; GSR sampling procedure; SEM analysis of particles; and daily, hands-on experience with SEM. Pre- and postworkshop written tests indicated that the participants gained the basic technical knowledge required. Most participants felt that a great potential for SEM use existed in their laboratories since it can also be used for many other types of trace evidence. Footnotes and a 10-item reference list are included. Appendixes contain a 63-item bibliography on forensic applications of the SEM, papers on the method, a list of participants, energy dispersive X-ray charts, and sample instruction sheets and course materials. For a report on the validity of scanning electron microscopy evidence, see NCJ 77119.