As a criminal investigator, you need to reconstruct crime scenes where firearms were used. Determining whether it was homicide or suicide, or who may have shot the firearm might be critical to a case.
Qualified forensic experts may be able to assist you with such investigations through the use of gunshot residue analysis. Gunshot residue (GSR) is particles that originate from partially reacted components of explosive primer and propellant as well as the bullet, cartridge case, and the firearm.
During forensic analysis, you can find GSR on the hands, hair and clothing of a person who has recently discharged a firearm, on an entrance wound of a victim, or on any other persons and objects that have been in the vicinity of the crime scene. Particles can be collected from a suspected shooter’s hand, for example, by using sample mounts (stubs) or adhesive tapes.
Depending on their shape, GSR particle size vary from sub-micrometers (μm) to several hundred µm in diameter. Unique GSR particles show a specific chemical signature; most commonly the combination of lead, barium, and antimony. In addition, GSR particles from lead-free type ammunition (Sintox) can be examined.
Scanning electron microscopes with energy dispersive x-ray spectroscopy allow the identification of very small amounts of GSR particles and the subsequent analysis of the surface morphology and composition of individual GSR particles with high accuracy.
ZEISS EVO Scanning Electron Microscope
Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) are well established techniques for the classiﬁcation of gunshot residue (GSR) in forensic examinations. Since the 1980s, the composition of many ammunitions has changed. Heavy metals have been avoided in order to comply with environmental standards, and stabilizers and plasticizers have been added during the manufacturing process for safety reasons. Thus, it has become more difﬁcult to classify the GSR particles. EDS analysis allows the identification of particles and classification of their characteristic chemical composition. Consequently, common GSR elements such as lead, antimony and barium can easily be detected. Whether you use adhesive stubs, tape or filter paper EVO, conventional SEM offers flexibility for any sample type. You can reliably detect GSR particles of ≥ 0.5 µm in size.
ZEISS Sigma Scanning Electron Microscope
Sigma is your field emission SEM for high quality imaging and advanced analytical microscopy. The Gemini objective lens design combines electrostatic and magnetic fields to maximize optical performance while reducing field influences at the sample to a minimum. Sigma’s best-in-class EDS geometry increases your analytical productivity, especially on beam sensitive samples. The short analytical working distance of 8.5 mm and a take-off angle of 35°allows you to obtain analytical data at half of the default probe currents and at twice the speed. The high stability of the Sigma column provides the means for fast and complete X-ray analysis and mapping. This is due to the fact that placing the detectors closer to the sample facilitates achieving complete shadow-free analytical results. a. With Sigma you can reliably detect particles < 0.5 µm in size and distinguish them from the environmental particles.