Ethan Groves presents to EAS on Paint Comparisons

On Tuesday, November 13th, 2018, Microtrace Research Microscopist Ethan Groves presented on forensic paint comparisons as an invited speaker at the Eastern Analytical Symposium (EAS). His talk, entitled “Examining Elemental Analysis by SEM/EDS in forensic paint comparisons,” was co-authored with Microtrace Senior Research Microscopist Christopher Palenik.

Groves discussed the analysis of several hundred automotive paint samples by scanning electron microscopy and energy dispersive X-Ray spectroscopy in an effort to produce better constraints on the analytical variables of SEM-EDS analysis that impact forensic paint comparisons, a more thorough understanding of compositional variations in automotive paints, and, ultimately, more rigorous methods of interpretation for forensic paint comparisons.

The talk was given as part of the Forensic Microscopy: “What is it? Who does it?” section of the conference, sponsored by the New York section of the American Chemical Society.

Abstract

Forensic paint analysis is among the more commonly encountered types of trace evidence. Elemental analysis using scanning electron microscopy / energy dispersive X-Ray spectroscopy (SEM-EDS) is a well-established technique that is often used to provide probative information in forensic casework. For the task of forensic paint comparison by SEM-EDS, there is little guidance concerning potentially critical analytical variables, including: sample preparation, data acquisition, and data evaluation. This presentation discusses the analysis of 300 automotive paint samples, which were analyzed on a layer-by-layer basis (totaling over 1200 layers) to better understand the impact of these variables and to develop a broader understanding of the range of elemental compositions that each layer of an automotive paint can span. From this dataset, selection criteria have been evaluated for establishing the range of elements that can be detected in automotive paint as a function of layer type (e.g., clearcoat, basecoat, primer). In combination, these experiments will lead to better constraints on the analytical variables of SEM-EDS analysis that impact forensic paint comparisons, a better understanding of compositional variations in automotive paints, and, ultimately, more rigorous methods of interpretation for forensic paint comparisons.

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