Forensic scientists have developed a new technique that can detect drug and explosive residue on fingerprint samples from crime scenes.
鈥淭hat information, the presence of drug particles, is an almost untapped resource,鈥� says at Loughborough University in the UK. That is because investigators use thin gelatine layers, called gel lifters, to lift fingerprints. These introduce chemicals to samples, making it difficult to identify trace amounts of drugs or explosives on them.
So, Reynolds and his colleagues used a technique called mass spectrometry to identify chemical compounds from gel-lifted fingerprints. First, they created fingerprints by placing their hands inside plastic gloves. Their fingertips left impressions on the inner surface of the gloves. They then turned the gloves inside out and handled small amounts of zolpidem, a common date-rape drug. This was to prevent their skin from absorbing the sedative. They then gently brushed off the excess from a contaminated finger before pressing it on glass, metal or plastic surfaces. They repeated this procedure 10 times with and without zolpidem for each surface.
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After gel-lifting the prints, the researchers extracted chemicals from them with a drop of liquid. They then placed the droplet inside a machine that used high-voltage electricity to suspend the particles in the air. This allowed them to identify zolpidem with 100 per cent accuracy for the first eight consecutive fingerprint touches.
鈥淥ur method allows us to detect all that information from these forensic gel lifts, which no one鈥檚 done before,鈥� says Reynolds. 鈥淎nd I think where it鈥檚 got real potential is to see if somebody had been handling a drug, especially in cases where they administered it to somebody to render them easy to assault.鈥�
It would also be helpful for investigators if this technique could detect drug metabolites, or molecules present in people鈥檚 sweat when they use drugs, says at the Pennsylvania State University. 鈥淚 don鈥檛 think at the level we鈥檙e working at the moment, it鈥檚 sensitive enough to do that,鈥� says Reynolds, though he and his team hope to get there in the future.
Drug Testing and Analysis
