Technology: Gold fingerprints lift the lid off illicit deals

日期:2019-02-28 10:05:03 作者:昌独鞍 阅读:

By JONATHAN BEARD in NEW YORK LAW enforcers in the US are using gold to lift fingerprints from difficult surfaces, like adhesive tape. Gold, which is useful where traditional methods for gathering fingerprints do not work, stains the proteins left on any surface that was in contact with the hand. The FBI and the Secret Service are using it to look for drug dealers and counterfeiters. Among other previously unsuitable surfaces that detectives can now test are styrofoam, floppy discs from computers and counterfeit dollars. George Saunders of the cell biology group at the Los Alamos National Scientific Laboratory in New Mexico, devised the process by adapting a biological technique used in immunological chemistry. He washes the fingerprint in a mixture of colloidal gold, a buffer solution of citric acid containing tiny particles of gold. After about 30 minutes, depending on the type of surface, he bathes it in a silver solution. Next, he puts an electrical field across the surface and an image begins to emerge as the gold is attracted to the protein in the fingerprint. The silver enhances the image by filling in around the gold, highlighting the fingerprint’s features. The next step is to transfer the prints from these surfaces to thin membranes of nitrocellulose, which are cotton-like polymers, and develop them. Saunders uses common reagents to develop and enhance any latent fingerprints that are found. ‘The developed prints are easily photographed, and the colour of the material on which the print is found doesn’t seem to matter,’ says Saunders. ‘The print will show up dark on light colours and light on dark colours.’ The technique works on both porous and nonporous surfaces. The first use of this method led to an arrest last March when the laboratory developed palm prints from a blank cheque that had been stolen from a military facility. ‘The Secret Service tried the standard methods and they didn’t work,’ says Saunders. ‘This one did.’ Unfortunately, one of the few surfaces that the technique cannot cope with is real American currency. ‘That’s because genuine bills are made up of a lot of flax and cotton which have a considerable amount of protein associated with them,