U.S. flag

An official website of the United States government, Department of Justice.

Utilization of Environmentally Acquired Very Small Particles as a Means of Association

NCJ Number
Forensic Science International Volume: 254 Dated: 2015 Pages: 26-50
Date Published
25 pages

Since very small particles (VSP) are ubiquitous in our environment but are virtually ignored by forensic science, this article describes an initial effort to exploit VSP for one specific application.



VSP range in size from an order of magnitude smaller than conventional trace evidence, down to the molecular level. Combinations of VSP provide an extraordinary, largely untapped resource for forensic associations and source attribution. The current study developed a method that tested for the SEM/EDS analysis of VSP recovered from the surfaces of carpet fibers – one of the most common types of trace evidence examined in crime laboratories. The goal was to exploit existing computer-assisted SEM/EDS methods to test whether VSP profiles could be useful to associate shed fibers with a source carpet.  Particles were harvested by washing and filtration onto polycarbonate filters. An SEM/EDS analysis protocol currently employed for environmental particle analyses was used, resulting in individual particle characterization based on fitting to reference spectra of 28 elements. Target Particle Types were defined based on the most abundant elemental profiles and used to bin the results for each specimen, resulting in a Target Particle Type profile. Within-carpet variability was assessed using Target Particle Type profiles from three different areas on each of nine carpets. Area profiles, defined from sets of ten fibers, were compared to profiles from individual fibers. Between-item variation was explored using a survey of an additional 12 carpets. Hundreds to thousands of VSP were found to routinely occur on individual carpet fibers. Their quantity and character were sufficient to associate fibers with their area of origin. Within-carpet variations showed roughly even distributions for most TPTs and between-carpet variations showed wide ranges in types and quantities of VSP. VSP are ubiquitous, present on or in virtually any item, and there is the potential for linkages among items of any type based on adhering VSP. Further fundamental research is indicated to better understand the underlying variability, usefulness, and limitations of this approach. (publisher abstract modified)

Date Published: January 1, 2015