Shooting distance determination by m-XRF—Examples on spectra interpretation and range estimation

The XRF's multiple element detection capability is especially useful for the detection of gunshot residue (GSR) of modern lead-free ammunition. An elemental mapping from milli-X-ray fluorescence analysis (m-XRF) can be used in an analogous way to the chemographic imprint to determine the shooting distance. As it is possible to take the mappings of all relevant elements into account, the shooting range estimation becomes more reliable. A numerical tool is presented to display the data and to help differentiate between shooting distances. From the nature of the samples, i.e. a small amount of GSR deposited on a highly scattering background some problems arise. Examples of some major problems in spectra interpretation are stated and examples are presented. Spectra interpretation cannot be fully automated and some points need to be verified by an experienced user.