Original URL: http://www.theregister.co.uk/2005/03/22/sweat_prints/

Sweaty palms? You're nicked, chummy

Trace elements can now reveal fingerprints

By Lucy Sherriff

Posted in Science, 22nd March 2005 12:10 GMT

Researchers at the Los Alamos laboratory in the US have developed a new way of detecting fingerprints, using the chemical elements left behind in fingerprint residue. That is sweat, to you and me.

When we sweat, our bodies excrete salts, such as sodium chloride and potassium chloride. These salts can actually be detected in fingerprints using a technique called micro-X-ray fluorescence (MXRF) which will pick out the constituent elements.

Fingerprints in glorious technicolour

The elements make it possible to "see" a fingerprint where the salts have been deposited in the patterns of fingerprints, the lines that forensic scientists call friction ridges.

Traditionally, forensic scientists dust a crime scene for prints, literally adding a layer of coloured powder to a surface. The dust sticks to sebum, an oily substance left behind by each finger, and enhances the contrast between the surface and the print's friction ridges. This technique does have its limitations, particularly when a surface is multicoloured, or highly textured.

The research team sees the technique as a companion to more traditional methods. They say it could be particularly useful for detecting prints left by children, because kids' hands don't leave sebum behind for the contrast enhancing agent to stick to. It is also a non-invasive technique, so any print examined using MXRF is left pristine for examination by other methods, such as DNA extraction.

Los Alamos scientist Christopher Worely, who presented the research to the American Chemical Society in San Diego, last week, said that the new method should not be regarded as a replacement for traditional fingerprint detection and collection. He stressed that some fingerprints will not leave behind enough of these trace elements to be seen using MXRF. ®

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