Linking Suspects to Crime Scenes with Particle Populations
Two researchers with a long record of research into the forensic value of very small particle populations examined cell phones, handguns, drug packaging, and ski masks from the San Diego County Sheriff’s Office to determine if such particles can make physical evidence more valuable in court cases.
December 11, 2017
David and Paul Stoney, two brothers who operate Stoney Forensic in Chantilly, VA, have long believed that the innumerable very small particles in the environment can be used to solve crimes. “Very small particles (VSP) are ubiquitous in our environment and are virtually ignored by forensic science,” the Stoneys said in the summary of their latest NIJ-supported study of such particles
“We move about in a soup that is a combination of [very small particles] that provides an extraordinary, largely untapped resource for forensic associations and source attribution,” they said. The point of this study was to test particles taken from actual pieces of evidence, apply established analytical and interpretive methods and determine the “evidential value” of such particles.
Their earlier research established the viability of using such particles for two important forensic purposes: matching an object found at a crime scene to a suspect’s vehicle or residence; and tracing the recent history of where an object has been. In this study, the researchers sought to determine the evidential value of VSP profiles found on handguns, cell phones, drug packaging, and ski masks. The samples tested were actual evidence held by the San Diego Sheriff’s Office.
The researchers used a combination of swabs and scanning electron microscope techniques to sample 30 handguns, 31 cell phones, 36 drug packaging specimens, and 32 ski masks. Overall, 82 percent of the VSP specimens recovered showed “sufficient variety and complexity in their VSP profiles to allow meaningful classification.”
After sampling and analyzing the VSP populations from the objects, the researchers said the data “were sufficient to permit quantitative associations among specimens.” The number of particles recovered was greatest from the plastic drug packaging, intermediate for the cell phones and firearms, and low for the ski masks. More efficient methods of sampling ski masks might be possible, but need further research, they said.
The Stoneys said their “entirely new approach to trace evidence” is enabled by this research. “The evidence type itself is actually acting as a carrier of the VSP signal that has resulted from its history of exposure,” they said. “Other items of evidence, of any type, that have shared a common history of exposure will also act as carriers of a closely related VSP signal. Using the same methodology employed in this project, VSP on a knife or tool left at a crime scene can, for example, be compared and linked with VSP from a suspect’s residence or from his pocket.”
The findings of their innovative work, they concluded, “provide a strong impetus to continue the research necessary to realize [VSPs] potential and transition this technology into operational practice.”
About This Article
The research described in this article was funded by NIJ cooperative agreement number 2015-DN-BX-K046, awarded to Stoney Forensic, Chantilly, VA. This article is based on the grantee report “Evidential Value of Particle Combination Profiles on Common Items of Physical Evidence,” (pdf, 22 pages) by David Stoney, Paul Stoney, of Stoney Forensic.
This research is part of a broader portfolio of trace evidence projects managed by NIJ Physical Scientist, Gregory Dutton., Ph.D. Find more information about other trace evidence research projects.
Cite This Article
National Institute of Justice, “Linking Suspects to Crime Scenes with Particle Populations,” December 11, 2017, NIJ.gov: https://nij.gov/topics/forensics/evidence/trace/pages/linking-suspects-to-crime-scenes-with-particle-populations.aspx
Date Created: December 11, 2017