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Application of Raman and Infrared Microscopy for the Forensic Examination of Automotive Clear Coats and Paint Smears

NCJ Number
Date Published
13 pages

This is the Final Research Report of a project that examined the potential of Raman spectroscopy as an alternative means of extracting distinctive information from an automotive clear coat, and it examined the possibility of developing procedures that generate automotive paint smears (e.g., clear-coat and color-coat layers mixed together or clear coat, color coat, surfacer-primer, and e-coat layers mixed together).



Modern automotive paints consist of a thin e-coat, primer, and color-coat layer protected by a thinner clear-coat layer. In some ”hit-and-run” offenses, a clear coat from the offending vehicle is the only layer of automotive paint recovered at the crime scene. The problem is that clear-coat formulations are too similar to provide a means of tracing one to a particular vehicle or manufacturer; however, recently published studies of pattern recognition methods applied to the infrared (IR) spectra of clear coats have indicated that information about the line and model of the vehicle can be obtained from these spectra. The complementary nature of Raman and IR spectroscopy and the importance of IE spectroscopy in forensic automotive paint analysis suggest that Raman spectroscopy will also have the potential to extract investigative leads from the clear-coat layer of an automotive paint. The binary classification studies performed demonstrated that all six vehicle assembly plants involved in the study could be identified based on their clear-coat Raman spectra. The report concludes that these results constitute direct evidence of the potential advantages of Raman for forensic automotive paint analysis. Paint smears were generated from 30 General Motors automotive paint samples that represented a variety of paint chemistries. Project publication list and 14 references



Date Published: January 1, 2022