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Differential Quantitative Analysis of Particles From the Contact Surfaces and Recessed Areas of Footwear

NCJ Number
Date Published
December 2017
20 pages
Findings and methodology are reported for a study that tested the ability of quantitative differential analyses of very small particles (VSP) on the contact surfaces and recessed areas of footwear to separate trace evidence signals attributable to different exposures.

This report presents four major findings of this study. First, contact surfaces of the footwear were universally dominated by VSP attributable to the last (third) site, as expected from previous research. Second, VSP recovered from the recessed surfaces of the boots showed major percentages of VSP attributable to the first and second sites of exposure; for all boots, this was just over 25 percent of the VSP. Third, a markedly different effect was found for the athletic shoes. Although there were detectable percentages of VSP attributable to the first and second sites of exposure, the amounts were much less than for boots, averaging only 13 percent. Fourth, when VSP were found attributable to the first and second sites, there was no clear trend for dominance of either the first or second site. Rather, it may be that the characteristics of the site was more of a factor. The researchers reason that the process of separating discrete signals of interest through quantitative differential analysis has the potential to extend the application of these methods to surfaces and items to which a mixture of sources has occurred. The study methods described encompass recovery of VSP from footwear soles by swabbing; particle isolation and mounting for microscopical analysis; polarized light microscopy (PLM); and data reduction and statistical methods. Data analysis is also discussed. A list of scholarly products produced or in process is provided.

Date Published: December 1, 2017