Firearm discharge residue

The NAA method for the determination of firearm discharge residue has been generally accepted, but applications have been limited to just a few laboratories. In the process of establishing NAA capability for the State of Illinois crime laboratories we re-examined the standard techniques (10). In the course of our work it became clear that post-irradiation is the cause of several constraints which have discouraged a more widespread use of NAA. The inherent time limitation due to the 87 min. half-life of 139Ba necessitates fast manipulations of radioactive solutions which in turn requires an experienced radiochemist. In addition to an ever present danger of overexposure and contamination, typically only a dozen samples can be irradiated per batch, which makes the method quite expensive. The developed statistical bivariate-normal analysis (11) is convenient for routine applications. With this in mind, a method was developed which a) eliminates post-irradiation radiochemistry and thus maximizes time for analysis b) accommodates over 130 samples per irradiation capsule (rabbit) c) does not require a collection of occupational handblanks and d) utilizes a simplified statistical concept based on natural antimony and barium levels on hands for the interpretation of data. The detailed procedure will be published elsewhere (15). 

Several techniques have been utilized for the detection of firearms discharge residue on the hands of an individual who has recently handled or discharged a weapon. Testing for the presence of nitrates proved unreliable and was discarded. Colorimetric tests for barium and antimony from primer composition were found to lack sufficient sensitivity for general application. 

Neutron activation analysis (NAA) with a rapid radiochemical separation has been the method generally used in recent years, but requires substantial investment, has high operating cost and limited availability. Modem flameless atomic absorption (AAS) instruments provide sensitivity approaching that of NAA and offer a viable alternative for the detection of firearms discharge residue. 

In 1959 Harrison and Gilroy (3) demonstrated the detectability of barium, antimony and lead in firearm discharge residue using a specific "spot" test for each element. Inadequate colorimetric sensitivity for barium and antimony (I4.) has severely restricted the use of the method as a field tool. 

The development of neutron activation analysis (NAA) as a sensitive and specific method of trace elemental analysis led to its application during the 1950 s for the detection of firearm discharge residue. Its ability to detect and identify very low concentrations of barium and antimony, elements associated with most primer compositions, was encouraging. 

A major problem confronting forensic laboratories interested in employing NAA is the scarcity of suitable reactor facilities. If firearms discharge residue analysis is to be widely employed, an alternate technique must be developed. Atomic absorption... 

Table III shows that two quite different analytical techniques, Flameless Atomic Absorption Spectroscopy and Neutron Activation Analysis, yield equivalent frequencies of detection of firearms discharge residue.

A "positive" firearms discharge residue result, as referred to here, is based upon occupational hand blank studies reported by several investigators (20,26,27,28). The 0.30 and 0.20 micrograin quantities for barium and antimony are conservative statistical estimates from average levels of these elements found in hand blank determinations. 

It should be further emphasized that the critical element in firearms discharge residue determination is Sb, because of its uncommon environmental occurrence. However, this common characteristic has led some investigators to consider using Sb alone for the determination of GSR (26). The two methods are in good agreement with regard to incidence of positives as indicated by Table III. 

Since both methods yield comparable results, which method should a laboratory use for firearms discharge residue detection Three factors must be kept in mind cost, turn-around-time and personnel requirements. 

In short, NAA is an excellent analytical tool, but for firearms discharge residue, FAAS is the more practical technique. 

Scott, H. D., Coleman, R. F. and Cripps, F. H. "Investigation of Firearm Discharge Residues" Atomic Weapons Research Establishment Report AWBE 0-5/66, England, (1968)... 

Examination of swabs and clothing from suspects for firearm discharge residues... 

Firearm discharge residue work is an important aspect of the overall workload. 

The gases, vapors, and particulate matter formed by the discharge of ammunition in a firearm are collectively known as firearm discharge residue (FDR) or gunshot residue (GSR) (Photograph 16.1). Anything present in the... 

Firearm discharge residue consists of a complex heterogeneous mixture that is claimed to be mostly particulate in nature.105 Particulate matter can be detected on a suspect, but the possibility of vaporized/gaseous products being adsorbed on to skin or clothing surfaces also exists. 

When a round of ammunition is discharged in a firearm, in addition to the projectile(s), firearm discharge residue is emitted, mainly from the muzzle but also from cylinder gaps, ejection ports, and other vents in the firearm. Some of this residue may be deposited on the skin, head hair, and clothing of the firer. 

Development of Firearm Discharge Residue Detection Techniques... 

G. Price, Firearms Discharge Residues on Hands, Journal Forensic Science Society 5 (1965) 199. 

S. S. Krishnan, K. A. Gillespie, and E. J. Anderson, Rapid Detection of Firearm Discharge Residues by Atomic Absorption and Neutron Activation Analysis, Journal of Forensic Sciences 16 (1971) 144. 

J. S. Wallace, Firearms Discharge Residue Detection Using Flameless Atomic Absorption Spectrophotometry, AFTE Journal 19, no. 3 (July 1987). 

Apart from various gases four types of particles have been detected in firearm discharge residue ... 

J. A. Goleb, and C. R. Midkiff, Jr., Firearms Discharge Residue Sample Collection Techniques, Journal of Forensic Sciences 20, no. 4 (1975) 701. 

With the emphasis on quality all systems were explored, both internal and external, with a view to ensuring that they could withstand close scrutiny from any source, that the possibility of cross contamination of suspects with explosives and/or firearm discharge residue is minimized, and that contamination risks within the laboratory are identified and minimized or eliminated. 

Unlike firearm discharge residue, each of the blank cartridges produced a limited range of discharge particle types. 

The work serves to illustrate the heterogeneous nature of firearm discharge residue particles and to clarify the types of particles detected. 

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