DNA readings from cat hairs have once again helped crack a homicide case — demonstrating the power of genetic pet databases to solve crimes.
The latest case involves a suspect in Britain who was convicted of manslaughter after prosecutors drew a genetic link between his pet cat, Tinker, and cat hairs found at the crime scene. Investigators took advantage of a database of DNA from 152 cats in Britain.
"This is the first time cat DNA has been used in a criminal trial in the UK," Jon Wetton, the University of Leicester geneticist who led the cat DNA project, said in a statement Wednesday. "We now hope to publish the database so it can be used in future crime investigations."
How the case was cracked
In July 2012, the dismembered torso of Hampshire resident David Guy was found on a Southsea beach, wrapped in a curtain on which eight cat hairs were found. Constables sent the hairs to California for analysis of the mitochondrial DNA, which is passed down from a mama cat to her kittens. Hairs from suspect David Hilder's cat were analyzed as well — and the tests came up with a match.
However, the prosecutors had to show how rare such a match might be for two random cats. That's when they brought in Wetton, who had already created a similar database for dogs while at Britain's Forensic Science Service. "We proposed creating a UK cat database from scratch," Wetton said.
The Hampshire Constabulary paid for a series of tests of blood samples from British cats, conducted by Ph.D. student Barbara Ottolini with the cooperation of vets across the country. When 152 cats were tested, only three of the samples came back with a mitochondrial DNA match to the hairs on the curtain, confirming that the genetic signature was uncommon.
Those findings were factored into the case against Hilder, a neighbor of Guy's who was convicted of manslaughter last month in Winchester Crown Court and sentenced to life in prison.
"This could be a real boon for forensic science, as the 10 million cats in the UK are unwittingly tagging the clothes and furnishings in more than a quarter of households," Wetton said.
Wetton acknowledged that Tinker's hairs weren't the only evidence in the case: The constables also found traces of Guy's blood at Hilder's Southsea residence. Nevertheless, the DNA evidence helped reinforce the prosecutor's case. The Associated Press quoted police as saying Tinker was alive and well and living with new owners.
Setting a precedent
Although the case of the curtained cat hairs appears to be a first for Britain, it's not the first time a homicide case has been solved thanks to cat DNA. In 1994, a Canadian woman named Shirley Duguay was found dead in a shallow grave. Her estranged husband, Douglas Beamish, had a white cat named Snowball.
Investigators determined that one of the key pieces of evidence in the case, a discarded leather jacket, was covered with Duguay's blood — and had cat hair in one of its pockets. DNA analysis of the cat hairs provided a match to Snowball's genetic signature. Meanwhile, experts tested about 20 other cats from the area to show that the signature was rare.
Beamis was convicted of second-degree murder and sentenced to 15 years in prison.
A researcher involved in that case, Robert Grahn of the University of California at Davis, said cats might be particularly well-suited for forensic analysis — due to their clingy hairs as well as their habit of licking themselves for grooming. "Cats are fastidious groomers, and shed fur can have sufficient genetic material for trace forensic studies," Grahn and his colleagues wrote in a paper published in the journal Forensic Science International: Genetics.
Since then, there's been growing interest in pet DNA databases for forensic purposes — and such evidence has figured in several prosecutions in the United States. In 1998, for example, dog DNA was used as evidence leading to the conviction of two Seattle men on charges of first-degree murder and animal cruelty.
More about pet forensics:
- Cat fur puts criminals behind bars
- Taking a bite out of crime with pet DNA
- Dog-poop DNA tests raise stench with renters
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.