Soil examination for a forensic trace evidence laboratory – Part 2: Elemental analysis

• XRF, SEM/EDX and LIBS are common in trace evidence forensic labs.
• XRF, SEM/EDX and LIBS are used to analyse Australian soil specimens.
• XRF, SEM/EDX and LIBS can be used to discriminate of forensic soil specimens.

Laser-induced breakdown spectroscopy (LIBS), X-ray fluorescence spectroscopy (XRF) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) are compared in terms of their discrimination power when applied to Australian soil specimens. SEM/EDX and XRF are frequently used in forensic laboratories for the elemental analysis of paint and glass, and for miscellaneous examinations. LIBS is an emerging technique for forensic applications, with a number of researchers promoting its use for the elemental profiling of glass fragments. In this study, 29 soil specimens were analysed, with 12 specimens coming from the Canberra area and the remaining 17 specimens from other sites around Australia. As very good discrimination results were obtained for each of the analytical methods, any of these elemental analysis techniques, available in a trace evidence laboratory, could be used as part of a wider examination protocol to differentiate soil specimens.