WVU experts have developed a new way to uncover clues from duct tape found at crime scenes. Credit: WVU Photo/Brian Persinger
A professor at West Virginia University is calling attention to an overlooked element of trace evidence: duct tape.
“Duct tapes, in particular, are used very often to gag victims,” said Tatiana Trejos, assistant professor in the West Virginia University Department of Forensic and Investigative Science. “So, when we have traces that are left, they can tell us about who was there, who tore it apart and so forth.”
The problem is, there’s no standardized protocol or industry accepted guidelines for the analysis of duct tape. Trejos hopes to change that. She and graduate student Meghan Prusinowski have developed a one-of-a-kind method that provides a systematic approach for comparing pieces of trace evidence that appear to be from the same source—including duct tape.
When a material like duct tape is separated into pieces, it leaves “fracture edges,” which can be evaluated and examined to see if there is a physical fit. A physical fit is putting the two fracture edges together and demonstrating that they have enough individual characteristics to indicate that they were once together, explained Trejos. This type of evidence tends to be reliable, especially given the random nature of edge fractures.
“It is very unlikely that we can reproduce all the microscopic features of a torn edge,” said Trejos. “We can tear apart thousands and thousands of pieces, and we have demonstrated it’s very unlikely that there will be, just by random chance, a perfect fit in pieces that were not once together.”
The new method allows examiners to qualify and quantify features and characteristics that are commonly observed during physical fit examinations. Then, the examiners follow the criteria to provide a score metric of how similar the tape edges are, estimate probabilities and use an Excel template to systematically document the features of the physical fit.
Testing the method, Trejos and her students found the error rate was extremely low in duct tape physical fit examinations. The next step, she said, will be to teach forensic examiners how to follow the method.
“Historically, examiners have been very good at correctly identifying fits,” Prusinowski said. “But until recently, there hasn’t been much research identifying what can cause misidentifications, and there really haven’t been many studies that recommend a particular method for edge comparisons.”
The team has already led a series of interlaboratory studies to test the method using practitioners involved in physical fit examinations for years or even decades; but there’s more to come.
Prusinowski said the established guidelines will also help researchers focus on pattern recognition in other trace evidence materials.
The next step will be to provide other forensic labs with the scientific foundation the West Virginia University team has established.
“They’ll have all the resources they need to present evidence in court,” Trejos said. “Because that can make the difference between sending an innocent person to jail or not.