Forensic science, the application of science to law, extends beyond studying DNA samples to include the microscopic analysis of more diverse bodies of evidence, such as gunshot residue, clothing fibers, handwriting samples, and car paint chips. The need to more accurately and rapidly identify and analyze crime-scene samples with high-resolution detail is increasing, as more sophisticated criminals and new types of evidence challenge existing forensics tools and techniques.
FEI has leveraged its technology expertise and leadership in high-resolution imaging and microanalysis to create powerful systems and applications that work together as complete forensic solutions. Working extensively with the worldwide forensics community to understand the unique challenges and application requirements of forensic science, FEI technical engineers and application specialists have designed and manufactured the next generation of forensic microscopy tools to help investigators maintain the evidentiary validity of the proof and the integrity of the samples.
Because forensics labs handle such disparate types of samples, FEI tools for forensics allow scientists to examine virtually any sample in an environmental scanning electron microscope (ESEM) chamber, so it can be analyzed in its natural state.
Forensic Platforms
The FEI Forensic Scanning Electron Microscope (SEM) [PDF] and the Gun Shot Residue (GSR) SEM [PDF] are flexible platforms that allow forensic specialists to focus on microscopic traces of evidence using imaging, comparison, and X-ray microanalysis (EDS) techniques.
The Forensic SEM [PDF] offers three imaging modes—high-vacuum, low-vacuum, and environmental—so samples can be analyzed in their natural state with no special preparation required, resulting in substantial time and cost savings. Traditional techniques of secondary electron and backscatter imaging and EDS can be applied. Even non-conducting, out-gassing, dirty, oily, or wet samples can be examined nondestructively; no coating, cutting, drying, cleaning, or manipulation is necessary.
The FEI GSR SEM [PDF] is engineered for the automated analysis and classification of gunshot residue. In addition to conventional, high-vacuum imaging, the GSR SEM enables specimen surface imaging in a gaseous environment or at varying sample chamber pressures for backscatter detection, elemental contrast, or topographic contrast. Gas in the chamber eliminates the charging effects of the uncoated sample, and dedicated detectors use gas to aid the imaging process. This application-oriented tool has a fully integrated software package to analyze and classify gunshot residue. Its high-precision, motorized stage can return to the field of interest and then center and magnify the selected particle for thorough analysis and reconfirmation.
Validation
A critical aspect of the SEM/EDS system, including GSR analysis, is validation to ensure reliable results when using the tools on a day to day basis. To ensure reliable results, the systems behavior needs to be diagnosed in fixed intervals. Special GSR test standards (Plano GmbH, Germany) are available and designed for the adjustment, calibration and validation of analytical SEM/EDS systems when used for automatic analysis of GSR particles. Synthetic GSR particles are randomly distributed on the sample, the amount of particles, as well as their size and location on the standard, are well defined. The sample was used by the European Network of Forensic Science Institutes (ENFSI) as a round robin test for GSR analysis. Special auto-validation software helps to diagnose the system for many vital points in order to guarantee a correct performance. The microValidator™ [PDF 221KB] reports any error or misalignment and is the perfect tool for diagnosing your SEM/EDS/GSR analysis system. It consists of an integrated specimen current meter, a multi-faceted calibration sample and the microValidator software.
Forensics Resources and Web Links
Explore the links below for more forensics resources available online: