Automotive paint analysis: How far has science advanced in the last ten years?

Abstract

The driver's criminal conduct of evading after a collision (hit-and-run) is a problem for law enforcement agencies worldwide. Witness reports or video images are not always reliable nor available. Fragments of paint left behind at the crime scene become essential for the criminal investigation process. This study reviewed publications about automotive paint analysis, published from 2010 to 2019. In each study, we evaluated: technique, paint layer, data analysis methodology, model validation, chemical characterization, samples degradation and origin (both their sources and their support bases - plastic vs. metallic). Of the techniques reviewed, infrared spectroscopy was the most commonly used technique for forensic paint analysis. The authors reported complementary or alternative techniques that have been used to analyze paint samples, such as optical examination, Raman spectroscopy and elemental analysis and even more rare or innovative techniques i.e. optical coherence tomography. We also detailed the various chemometric techniques that have been employed when analyzing the resulting spectra. In summary, the information collated in this study will provide researchers that intend to create automotive paint databases for forensic purposes, with a suite of instrumental techniques, analytical methodologies and data interpretation protocols that can be incorporated into a database.