CHAPTER 7: Scanning Electron Microscopy in Forensic Sensing

The usefulness of scanning electron microscopy for forensic applications was noticed as soon as the first commercial instrument became available in 1965. This was firstly due to better resolution, depth of focus and contrast than in the optical microscopes being widely used for routine imaging tasks. Soon, other properties of the scanning electron microscope were utilized for enlightening of crimes, i.e. its ability to simultaneously produce several electron beam-induced signals from the specimen, which generate images of surface topography and provide information on the material composition. A combination of scanning electron microscope with energy-dispersive X-ray microanalysis proved to be the most versatile technique in testing materials, as it is capable to process each specimen signal by various contrast-enhancement methods, such as line scanning, area mapping, qualitative and quantitative elemental analysis as well as automation of some investigative processes. Gunshot residue particles, collected by the glue-lift technique, are model examples of the detection of the evidence of crime. In physical matching and non-destructive analyses of other trace evidence, such as hair, fibres, paint, glass, minerals, metals, some microorganisms and biological specimens, chemical substances, etc. the scanning electron microscope and energy-dispersive X-ray microanalysis is the most efficient of all microbeam technologies.