Gunshot Residue

It is well established that a large percentage of Gunshot Residue (GSR) particles that have been deposited onto a person’s hands will be lost within a few hours of exposure. The particles are not adherent to the skin by some glue-like property. Neither are they embedded in the skin. They are merely lying on the surface of the skin and are, therefore, easily removed by everyday activities but given their extremely small size they readily become trapped in the microscopic folds of the skin or drop down into hair follicles

Swabs are typically obtained from the hands, face and hair of the suspect and are therefore only of particular relevance when there is a short timescale between incident and apprehension.

In the US there is considerable debate about the reliability of GSR, particularly in cases where there is perhaps a single particle present on, for example, an individual’s hand. It is reasonable to suggest that this work area is undergoing great scrutiny worldwide and it is likely that in the coming years there will be changes to the presentation and significance of GSR evidence.

The samples are analysed by Scanning Electron Microscopy / Energy Dispersive X-ray analysis in order to examine any particles present that are collectively called firearms discharge residues. These particles have distinctive and often unique chemical compositions and also when viewed under high power microscopy have characteristic surface features or morphology.

GSR is made-up of unburnt particles of the propellant and metallic particles that have been formed from the primer compound as well as from the cartridge case and bullet. Certain combinations of metallic elements in a particle are considered to be highly characteristic of GSR. There are five types of primer residue commonly encountered and the abundance of them is the primary method of assessment in a case such as this.

Bericon is able to offer an extensive review of not only the analysis of any recovered particles but more importantly assess the significance of these particles in relation to their abundance, location and the possibility that they may have been transferred by cross-contamination, a subject that continues to haunt the forensic community and particularly so when the evidence of interest is at the microscopic level, as is the case in most GSR cases.