UT-ORNL Researchers to Uncover Mysteries of Fingerprints

KNOXVILLE — University of Tennessee and Oak Ridge National Lab researchers are setting out to solve mysteries about a common forensic tool — fingerprints.

Working under a grant from the U.S. Department of Justice, UT-ORNL joint professor Mark Dadmun is researching ways to make it easier for forensic scientists to develop fingerprints.

Most fingerprints on objects are invisible to the human eye, but Dadmun is analyzing a technique that has been used by forensic investigators for about 20 years to make them visible. The investigators place an object with a faded fingerprint above a heated dish of superglue, and as the fumes reach the object, the print begins to build, seemingly out of thin air. Even more of a mystery, according to Dadmun, is how this works and why the process worked better in a very humid environment.

“Investigators have known and used the process for years, but there was not a full understanding of why it was so effective,” said Dadmun, a professor of chemistry at UT.

Dadmun explains that molecules of cyanoacrylate, the main ingredient in superglue, bond to the fingerprint in ever-larger chains known as polymers. As the chains tangle together and grow, they become visible to the eye, essentially reconstructing the fingerprint from the ground up.

Investigators had always assumed that since the process worked faster in a humid environment, that water was the key to the growth. However Dadmun’s research has shown that water does not cause the superglue to grow off of the faded prints.

“It’s not the water,” said Dadmun. “Water probably plays a role when you’re using superglue as a glue, but as a vapor, there’s some other mechanism.”

Dadmun works closely with Linda Lewis, an Oak Ridge researcher in chemical sciences, whose work looks at new ways to rebuild fingerprints that have faded over time.

Fingerprints consist of sweat and oil from the skin which contain numerous components, many of which have a part called carboxylates, and these are the main actor in starting the growth of the polymer from the print.

It also appears that these carboxylates degrade quickly. Especially when exposed to ultraviolet radiation from the sun’s rays, the carboxylates break down swiftly — fingerprints are often difficult to develop if left in the open for more than a few days.

Lewis has found, however, that a fingerprint that is useful to investigators can be made visible if an old print is exposed to acetic acid — essentially a very refined version of household vinegar. It appears that the carboxylates that have broken down are replenished or rebuilt by the exposure to acetic acid, which also contains a carboxylate group.

Dadmun and Lewis have worked closely with members of the law enforcement community as they have conducted their research, making presentations at forensic conferences and publishing their research in forensic journals.

“They’re very appreciative of being kept up to date on our research,” said Dadmun. “Our hope is to make this practical and useful to them, so we try to stay in contact about how things progress.”

As their research continues, Dadmun and Lewis are focusing on creating methods that will allow forensic scientists to recreate more fingerprints that are found at crime scenes than is currently possible, as well as ensuring they are admissible as evidence in court.

Some of the techniques are already being attempted in the field, and the two plan to continue to work with law enforcement agents.

The UT-Oak Ridge partnership combines the strengths of UT and ORNL to further the mission of both institutions. From joint faculty and research to four new joint institutes in biological science, computational science, neutron science and advanced materials, the partnership is a research and economic driver for East Tennessee and the nation.

Contacts:
Jay Mayfield (865-974-9409, jay.mayfield@tennessee.edu)
Mark Dadmun (865-974-6582, dad@utk.edu)