Examination of Automobile Paints by Laser Beam Emission Spectroscopy

Abstract

Abstract An analysis was performed on 112 paint chips of various colors from wrecked, late model automobiles. A laser beam microprobe was used in conjunction with an emission spectrograph in order to determine the applicability of the laser microprobe in forensic paint analysis and the specificity of the emission spectrograph in paint analysis. The emission spectrograph was employed to determine the relative abundances of elements in the surface layers of the paint chips. The laser microprobe attachment permitted the analysis of very small paint chips and the analysis of the surface layers of the multilayer paint chips. The results indicated that of the 112 paints analyzed (a) 11 pairs of paints which were physically identical could be distinguished by the emission spectrograph, (b) 4 pairs of paints which were physically identical were also identical by the emission spectrograph, and (c) 3 pairs of paints which were not physically identical were identical by the emission spectrograph. From the results it was concluded that, although the elemental composition cannot individualize a paint chip, it is a useful forensic technique when supplemented with a microscopic examination.