During the investigation of any crime where a firearm has been discharged there is a need for gunshot residue (GSR) analysis, an expensive and lengthy process that is often seen as a drain on forensic laboratory resources.
The most commonly used methods of GSR detection are presumptive tests (nitrate detection) and SEM-EDX, used for imaging and elemental analysis of particles.
Currently both of these methods have significant drawbacks when it comes to GSR screening; nitrate detection is unspecific due to the near ubiquitous presence of nitrates in many commercial products, while SEM-EDX is not suited to the screening of a large number of samples due to its being both costly and time-consuming.
A recent study of GSR screening methods by the Centre for Material Science and Engineering at Cranfield University, UK has shown that that the Foster + Freeman ECCO can provide forensic examiners with a high-speed and consistently accurate solution, particularly when large numbers of samples are submitted for analysis.
Using Laser Induced Breakdown Spectroscopy (LIBS) the ECCO has been used to rapidly screen swabs from suspects’ hands for elements consistent with GSR, such as the detection of Barium (Ba) and Lead (Pb). Once a screened sample has tested positive for GSR it may then undergo lengthier and more detailed analysis if required.
The spectrum below of a GSR was recorded in less than 1 second, and clearly reveals peaks due to Barium (Ba) and Lead (Pb) – consistent with GSR.
The Foster + Freeman ECCO is a multi-purpose instrument commonly used for the analysis of glasses, metals, and soil, but which also has many other possible applications.
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