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"The latest in high-tech crime scene investigation is a \"fluorescent tag\" that can help identify fingerprints on bullets, knives and other metal surfaces by creating images that are accurate to the nanoscale.\nA significant portion of crime scene investigation involves searching for what are called \"latent fingerprints,\" or deposits of secreted sweat and natural oils transmitted by touch onto a flat surface, which are usually invisible to the naked eye.\nThe ridges on human fingertips, also called epidermal ridges or friction ridges, make the lines, whorls and swirls in these latent fingerprints. These patterns are virtually unique to each individual person (the chances of two people having the same prints are 64 billion to one), which makes fingerprints an excellent way to identify who was present at a crime scene. \nSEE ALSO: Crime Busters Embrace Social Media\nOne of the most common current methods of imaging and analyzing these fingerprints is called dusting. You've probably seen it in movies or on television \u2014 investigators brush fine powder onto the fingerprint, then \"lift\" the print by applying and then peeling off tape. The imprint of the powder, in the shape of the fingerprint, is preserved on the tape and can be taken to a lab for further analysis.\nUniversity of Leicester scientists, however, say that only 10% of latent fingerprint images drawn from crime scenes are complete enough to be used in court.\nThis is partly because latent fingerprints are often incomplete or smudged. Current techniques for imaging latent fingerprints, such as dusting, also run the risk of damaging the fingerprint before it can be accurately recorded.\nSEE ALSO: 10 Most Awkward Technology Terms\nTo that end, the scientists have developed a new method for imaging latent fingerprints that uses a film made of electroactive polymers \u2014 long, complex molecules that change shape in response to surrounding electric currents.\nThe researchers' findings were published on July 2 in the Royal Society of Chemistry's journal Faraday Discussions.\nDue to the polymers' electroactive properties, this film can be applied via an electric current, which drastically reduces the risk of damaging the fingerprint before an accurate image can be drawn, the researchers say.\nSEE ALSO: 8 Safety Basics College Students Need to Know\nWhen the electric current is directed at a latent fingerprint, the film adheres to the gaps between the swirls of deposits that comprise latent fingerprints, and not to the deposits themselves. That's because these deposits are insular, meaning they don't conduct electricity.\nThe polymers that comprise the film are also electrochromic; that is, when exposed to an electrical charge, they change color.\nThe result is an inverted image, or negative, of the fingerprint that is highly detailed and visible, making it easy to photograph and analyze, according to the University of Leicester team.\nThis technique is accurate to the nanoscopic scale; even a few molecules of sweat and oil are enough to prevent the polymer film from being transmitted. \nSEE ALSO: 10 Ways You're Using Nanotech Right Now (And Don't Even Know It)\nFurther, the scientists have improved on this technique by adding fluorophores, molecules that glow when exposed to a certain type of light, to the film. This will allow crime scene investigators to tweak the coloration of the fingerprint image in order to achieve the best possible contrast with the background surface.\n\"[Fluorescent tags] sound like a very interesting approach,\" said Christopher Hopkins, director of the Forensic Science Program at the University of California, Davis and a former FBI investigator, who is not associated with the University of Leicester research.\nHowever, he added, \"Over the course of my career, we see a lot of people developing new techniques [for crime scene investigation], and sometimes we adopt them, and a lot of times we don't, for a number of reasons.\"\nSEE ALSO: Who's Liable for Crimes Committed With a 3D Printed Gun?\nAccording to Hopkins, whether or not investigators adopt the fluorescent tag depends on how expensive the process is, how long it takes and whether it can be shown to provide more accurate results than current methods.\nThe technique is \"certainly a laboratory approach,\" he said. \"That doesn't mean it can't be used. It just has to be used in a lab setting, which we do quite frequently with a lot of the evidence we collect at crime scenes.\"\nHopkins was also skeptical of the technique's applicability on weapons.\n\"Traditionally, we have very low success at finding fingerprints on weapons,\" he said of his 25-year career with the FBI. \"With firearms specifically. We don't know why that is.\"\nImage courtesy of University of Leicester"^^<http://www.w3.org/2001/XMLSchema#string>
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