A team from Imperial College London's Department of Chemical Engineering has developed a new fingerprinting technique that could detect the diet and sex of a suspected criminal. The technique collects fingerprints along with their chemical residue and keeps them intact for future reference. Chemical residues contain a few millionths of a gram of fluid. Conventional fingerprinting techniques distort or destroy vital chemical information with no easy way of lifting residues for chemical imaging.

The use of gel tapes, a commercial gelatin based tape, provides a simple way to collect and transport prints for chemical imaging analysis. Once lifted, the prints are analyzed in a spectroscopic microscope. The sample is irradiated with infrared rays to identify individual molecules within the print to give a detailed chemical composition. The information is processed by an infrared array detector that chemically maps the residue. This process builds up a picture, or chemical photograph, and provides the most comprehensive information obtained from a fingerprint.

The information is enough to determine clues about a person beyond their fingerprint, such as identifying traces of items people came in contact with including gunpowder, narcotics, and biological or chemical weapons. It could also highlight specific traits in a person. A strong trace of urea, a chemical found in urine, could indicate a male, while weak traces could indicate a female. Specific amino acids could indicate if the suspect was a vegetarian or meat-eater.

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