Using integrated SEM-EDX technology to provide automatic, rapid, and validated results.

As the volume of cases grows and forensic crime labs’ budgets shrink, lab operations management, technicians, and litigators are all looking for answers related to gunshot residue (GSR) detection, identification, and characterization. Lab operations need high throughput solutions that require little oversight or expertise, yet maintain a high degree of reliability. Lab technicians need easy to use platforms that generate accurate results and reporting that provides information and knowledge, not reams of data. And, above all, litigators need validation of that reporting and those results to give them the confidence they need to go to court and to ensure that those results will stand up under cross examination at trial. Integrated scanning electronmicroscopes with energy X-ray dispersive Spectrometers (SEM-EDX) offer platforms that not only provide GSR results, but further validate those results through a series of checks and balances; offering the answer that all three audiences are looking for.

SEM Technology and GSR
SEM-EDX systems are commonly used for imaging comparison and X-ray microanalysis of trace evidence samples including tool marks, ink, paper, fibers, hair, and

paint coatings. Back in the late 60s forensic laboratories in London started to use Scanning ElectronMicroscopes (SEM) for the manual detection and analysis of Gun Shot Residue particles on a routine basis. Forty years later, SEMs are still used in laboratories worldwide for the detection of GSR particles. Technological advances, including the integration of Energy Dispersive Spectrometers for elemental analysis (EDX) and a software platform for automated detection, relocation, confirmation, and reporting, have made this the go-to technology for EDX analysis and imaging of samples collected from suspect shooters.

Typically,GSR particles (Figure 1) are composed of lead (Pb), barium(Ba), and antimony (Sb), and commonly range in size from0.5 to 10microns.They have varying morphologies and surface textures, but the vast majority are generally spherical in shape. Ammunition can also be manufactured without lead. Lead-free ammunition is becoming more prevalent as manufacturers use lead-free or low-lead propellants to avoid the toxicity of lead .Aluminum(Al) and strontium(Sr) are often used in lead free cartridges. In addition, Sintox® GSR particles are characterized by spheroidal particles mainly consisting of titanium(Ti) and zinc (Zn).