The fingerprints, until now, were significant only for the identification of a person, but U.S. researchers have developed a new technique that can now help forensic experts discover much more than the identity of a person.

The newly developed technique for analyzing fingerprints can now help forensic experts identify what a criminal or terrorist suspect has touched. For example, if a person handled illicit drugs, explosives, poisons or other materials, there could be enough left in a fingerprint to spot them, a team of US researchers explain.

Lead researcher R. Graham Cooks, an analytical chemistry professor at Purdue University, and colleagues, who came up with a method of discovering chemical substances that reside in fingerprints, detailed their laboratory technique in Friday’s issue of the journal Science.

In their report, Cooks described how the new laboratory technique, called desorption electrospray ionization, or DESI, could find a wider application in crime investigations.

The new fingerprint analysis method involves spraying a tiny amount of solvent, either water or water and alcohol, that has been electrically charged, onto a fingerprinted surface and then analyzing the droplets that scatter off the print.

The droplets dissolve compounds in the fingerprints and splash them off the surface, which are then identified by a device called a mass spectrometer. The technique provides a two-dimentional "chemical image" of the fingerprint, allowing researchers to detect minute traces of compounds that were on the fingertips of the person who left the print.

"The classic example of a fingerprint is an ink imprint showing the unique swirls and loops used for identification, but fingerprints also leave behind a unique distribution of molecular compounds," Cooks said. "Some of the residues left behind are from naturally occurring compounds in the skin and some are from other surfaces or materials a person has touched."

Scientists hope this new method will enable the police identify which fingerprints belong to the the person who committed a crime and who have just touched objects at the crime scene.

In addition, the technology can be used to uncover fingerprints buried beneath others.

"Because the distribution of compounds found in each fingerprint can be unique, we also can use this technology to pull one fingerprint out from beneath layers of other fingerprints," said Demian R. Ifa, a Purdue researcher and co-author of the report. "By looking for compounds we know to be present in a certain fingerprint, we can separate it from the others and obtain a crystal clear image of that fingerprint."

The research that was performed within Purdue's Center for Analytical Instrumentation Development located at the Bindley Biosciences Center in Purdue's Discovery Park will come into practice in about two years, when it will be ready for mass usage.

Cooks' device, DESI, has been commercialized by Indianapolis-based Prosolia Inc., which along with the Office of Naval Research funded the research.