Laser-based fingerprint analysis could help detect forensic residues

Fingerprints have been used by police forces to identify people present at a crime scene for almost 150 years. But the marks left behind by fingers can hold more information than just the identity of the person who made them. Residues of any substances the person had been in contact with can also be transferred to surfaces they touch — but recovering and identifying those substances can be very difficult.

Researchers from Louisiana State University in Baton Rouge have now devised a method which, they believe, could help considerably with this problem. Inspired by team member Eden Camp’s time interring with the Louisiana State Police Crime Lab, chemistry professor Kermit Murray and postdoc Fabrizio Donnarumma applied their expertise in using infra-red lasers to lift minute layers of tissues for bioanalysis to the problem.

In a paper in the Journal of The American Society of Mass Spectrometry, Murray’s team describes how they found they could use their laser equipment to ablate away fingermarks from a surface, suck the resulting vapour into a thimble-sized filter system and then subject these captured materials to techniques such as gas chromatography of mass spectroscopy to identify what substances were present. The ablation works by rapidly and specifically vapourising any water in the fingermark, carrying any other trapped material off the surface. This preserves the integrity of chemical residues, Donnarumma said.