Characterization of Paint Fragments by Combined Topographical and Chemical Electron Optics Techniques

Scanning electron microscopy is providing increasingly definitive solutions to criminal problems since its commercial debut in 1965. This has been due to the ability of the scanning electron microscope (SEM) to simultaneously produce several electron probe‐induced signals from the specimen, which generate readily interpretable images of surface topography and material composition. The successful applications of these signals are determined by sample preparation and instrumental parameters. No other microbeam technology combines high resolution (2–5 nm) of the topographic (secondary) electrons with large depth of field for three‐dimensional viewing. The SEM is indeed ideal for stereomicroscopy. The versatility of the SEM stems from its additional capability to process each specimen signal by various contrast enhancement methods, such as line scanning, deflection modulation (DM), area mapping, etc. These methods allow an intuitive, stylistic, and synthetic analysis of the image and are ideal for quality control analysis. Digital SEMs have pioneered in automated image processing and unattended search and analysis of particulates. The combined SEM and energy‐dispersive X‐ray microanalysis (EDX) is the most definitive technique in testing for gunshot residue (GSR) particles, collected by the glue‐lift technique. In the analyses of other trace evidence, such as hair and fibers, in physical matching, and in nondestructive elemental analysis of physical evidence, the SEM/EDX is the most efficient of all microbeam technologies. From firearms, bullet wounds and human bones, to plants, pollen and fungi, the list of criminal evidence examined by SEM/EDX is endless. However, the SEM/EDX is not ideal for quantitative analysis of elements present as traces (<1% w/w). The SEM lacks the three‐dimensional sectioning abilities of scanning beam confocal microscopes. The imaging capabilities of the SEM surpass these limitations. The SEM is, therefore, a major tool in forensic research and investigation.

Scanning Electron Microscopy in Forensic Science

Basu

2000

X‐Ray Fluorescence in Forensic Science

Roux

Lennard

2000

This article describes the applications of X‐ray fluorescence (XRF) as an analytical tool in forensic science, including limitations and practical aspects. The use of XRF is specifically discussed for the forensic analysis of materials of forensic interest such as metals, gunshot residues (GSR), paint, glass, soil, fibers, plastic and general polymers, and miscellaneous types of evidence. Recent developments such as micro XRF and total XRF are also described. These specialized techniques have highly desirable characteristics for the elemental profiling of a wide range of forensic samples, and hence it can be anticipated that they will find increasing use in forensic laboratories in the future.

X‐Ray Fluorescence in Forensic ScienceUpdate based on the original article by Claude Roux and Chris Lennard,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

Roux

Taudte

Lennard

2013

This article describes the applications of X‐ray fluorescence (XRF) as an analytical tool in forensic science, including its limitations and practical aspects. The use of XRF is specifically discussed for the analysis of materials of forensic interest such as metals, gunshot residues (GSRs), paint, glass, soil, fibers, plastic and general polymers, documents, and miscellaneous types of evidence. Developments such as biological tissues micro‐XRF, 3‐D micro‐XRF — an adaptation of micro‐XRF — and total XRF are also described. These specialized techniques have highly desirable characteristics for the elemental profiling of a wide range of forensic samples, and hence we can anticipate that they will find significant use in forensic laboratories in the future.