In this interesting study, researchers from Chile and Spain have been able to use X-ray diffractograms of gunshot residues (GSR) to infer shooting distance. The shooting distance is a crucial parameter in solving criminal cases since it provides indications, for example, to separate normal suicidal cases from other shootings, such as self-defense, burglary, deterring, homicide etc…  

The experiment has been performed by collecting a set of GSR from shooting at various distances. By collecting the X-ray diffraction pattern of each residue from the shootings, it was possible to find correlations between the pattern and the shooting distance. By making use of Multivariate Partial Least Square Analysis, it was possible to have a good correlation and small prediction errors of about 3 and 7% when using one gun for the prediction and the predicted value, but also still a good estimate (error of about 14 %) when combining the results of two guns, showing that it would be possible to estimate the shooting distance also when the gun used for the shooting is not available.  

This is another example of the importance of XRD in forensic and criminal analysis, see also, for example, the National Geographic article featuring an Empyrean diffractometer as “state-of-the-art machinery uses x-ray diffraction techniques to precisely identify substances such as methamphetamine or explosives”.