Analysis of cat hairs was recently crucial in prosecuting a criminal in a grisly murder case in the U.K. Eight cat hairs discovered on the dismembered torso of David Guy led to the conviction of his neighbor, David Hilder, who had been the main suspect in the case. Last month, Wilder was given a life sentence for manslaughter by Winchester Crown Court.
Cat DNA is “less specific than in humans, as the domestication of the animal has meant fewer genetic variants are present,” says the Independent. Some forms of human DNA found at crime scenes can actually “provide one-in-a-billion matches.”
But cat DNA still has distinctive features. Each cat hair contains two kinds of DNA, “nuclear DNA” that is specific to individual cats and can be detected in the roots of some larger hairs and “mitochondrial DNA,” which all maternally related cats share and which is detectable even in the finest hair shafts.
The Veterinary Genetics Laboratory at the University of California, Davis, has been using DNA from animals to assist in catching criminals for more than a decade. In one case, the lab traced blood from the scene of a nightclub stabbing in London to the bull terrier of the murder suspect.
Last July, Guy’s remains were found on Southsea beach; they were wrapped in a curtain on which authorities found cat hairs. The cat hair found on Guy’s body was initially examined by a U.S. lab and found to match with those of Hilder’s cat, Tinker, and not with those of 493 U.S. cats.
Police then sought to test cats in Britain.With the assistance of a doctoral student, Barbara Ottolini, Jon Wetton of the University of Leicester created a database of 152 samples of cat DNA. Wetton collected these from a firm that analyzes blood samples taken from cats and reveals their age, gender and (via their post code), the region where they live. 23 samples were taken from cats in Southsea and another 129 from cats throughout the country.
Out of these, three samples matched the cat hairs found at the crime scene. Tinker’s genetic make-up was actually rather rare and is only found in a third of cats; accurate matching for the other two-thirds is far more complicated, Wetton says.
Wetton had previously helped to create a similar database using dog hairs for the Forensic Science Service. He hopes that the cat DNA database might be published for use in future crime investigations. As he comments, 10 million U.K. cats like Tinker “are unwittingly tagging the clothes and furnishings in more than a quarter of households.”
The cat DNA database, which could also possibly be used in cold cases, will be published in a forensic science journal this year or next.
As for Tinker, who provided the essential evidence to convict Guy: the cat has reportedly found a new home and, according to police, is doing well.
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Photo via Bert Dickerson/Flickr
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