Gunshot residue is actually a compound containing either two or three particles commonly found in gunshot residue or primer residue. Examiners will say that particles with lead, antimony and barium present are indicative of gunshot residue while particles with two of the three particles are consistent with primer residue. The report issued by Hamilton County’s laboratory will state that two element particles “are found in primer residue, but also may originate from other sources.” For this reason, the use of gunshot residue is no longer accepted by many crime scene laboratories and forensic scientists.
The possibility of transfer of particles resulting in the contamination of the hands or clothes tested creates another area for challenge. All particles containing lead, antimony, or barium are very large. Additionally, these particles persist almost indefinitely. Furthermore, because the particles are rather large, they can easily transfer from hands, firearms, and furniture to clothing. If particles consistent with gunshot residue are found on hands, it indicates the person (a) had discharged a firearm, (b) had been near a discharged firearm, or (c) had come into contact with something that had gunshot residue on it. If particles are found on clothing, it indicates that the item (a) had been worn while a person discharged a firearm, (b) had been near a discharged firearm, or (c) had come into contact with something that had gunshot residue on it.
 Bykowicz, Lawyers Call City Analysis of Gunshot Residue Flawed, Baltimore Sun, Mar. 5, 2005; Orrick, Anoka Judge Rejects Gunshot Residue Evidence, St. Paul Pioneer Press, July 13, 2006 (quoting Judge Hall: “This court is not convinced that the relevant scientific community has a generally accepted standard for interpreting what conclusions can be drawn from GSR testing and analysis. . . . It is clear that significant questions exist . . . Concerning how many particles are required for there to be a positive test.”)
 See Summary of FBI Laboratory’s Gunshot Residue Symposium, May 31-June 3, 2005 available at http://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/july2006/research/2006_07_research01.htm (last visited Nov. 21, 2011)
Contributed by Andrea Kendall