Unique bacterial profiles give criminals another reason to wear gloves. Bacteria may one day help crime scene investigators catch criminals dirty-handed. Having found previously that everyone’s hands carry a unique bacterial population, researchers at the University of Colorado in Boulder have now shown that the mix of microbes left on a computer keyboard can be used to tell if a particular person had used it.
Their tests, reported online the week of March 15 in the Proceedings of the National Academy of Sciences, raise the possibility that hand bacteria could potentially serve as a new type of fingerprint. Noah Fierer and his colleagues wondered if bacteria could be used in forensic tests when fingerprints fail, such as when the prints are smudged or evidence consists of fabric or other soft surfaces that don’t lend themselves to fingerprinting. After all, says Fierer, “you only need to smudge a fingerprint, but you can’t sterilize a surface just by wiping it off.”
Fierer and his colleagues swabbed the hands of three people and took samples of bacteria from keyboards used exclusively by each of the three. The researchers then created DNA profiles of bacterial populations from the hands and keyboards. The bacteria on an individual’s keyboard closely matched bacteria on their hands, the team found. And the bacterial DNA remained useful for at least two weeks after swabbing. Fierer agrees that much more testing is needed to determine whether bacterial fingerprinting will be a useful forensic tool. The researchers are now trying to determine how many times people must touch objects to leave their bacterial signatures behind and whether bacterial fingerprints can be lifted from cloth or other soft surfaces.
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