Homeowners buy expensive alarm systems, tamper-proof locks and other items to protect their property, but a new study points to a less obvious crime-buster: cat fur shed by fastidious felines that might be living in the home.
An international team of scientists has just established an extensive DNA database that will permit cat fur to be used more often and accurately as forensic evidence.
Fur from a fluffy, white house cat has already been used in a murder trial. The accused, Douglas Beamish of Canada, had cat fur stuck to one of his pockets in a discarded jacket. The fur was genetically linked to victim Shirley Duguay's cat, Snowball. The evidence helped to convict Beamish of second-degree murder, leaving him with a 15-year prison sentence.
"The increasing popularity of the domestic cat as a household pet has unknowingly fostered the distribution of potential crime scene evidence across millions of households," according to Robert Grahn, lead author of the paper that has been accepted for publication in the journal Forensic Science International: Genetics. "Cat fur obtained from a crime scene has the potential to link perpetrators, accomplices, witnesses and victims."
"Cats are fastidious groomers, and shed fur can have sufficient genetic material for trace forensic studies, allowing potential analysis of both standard short tandem repeat (STR) and mitochondrial DNA regions," added the researchers.
The case involving Snowball used the STR method, which looks at particular markers that have been mapped in the cat genome. The new database, however, focuses on mitochondrial DNA (mtDNA), which is genetic material inherited from one's mother.
Mitochondrial DNA is useful in forensics primarily due to two properties. First, it has a high mutation rate, permitting more individuality between samples. Second, its genes exist in high amounts, even though mtDNA comprises less than 1 percent of the total DNA within a cell. While nuclear DNA is optimal for identifying individuals, mtDNA has proven to be a good alternate choice.
Grahn, a scientist in the Department of Population Health & Reproduction in the School of Veterinary Medicine at the University of California at Davis, and his team collected DNA samples from hundreds of cats from 25 distinct worldwide populations and 26 breeds. The samples came from drawn blood, cheek swabs and tissues collected during routine spay and neuter surgeries.
A prior study documented 174 mtDNA cat sequences. Together, the research has produced an extensive database consisting of 1,394 cat sequences that could be used by criminal investigators.
Grahn and his team point out that, aside from such mtDNA matching, nuclear DNA may also be found on cat hairs that still retain their root bulbs, or on skin particles that might stick to the oily fur when cats groom themselves.
These natural oils, along with static electricity and the sheer volume of fur, mean that people who enter a property with a resident cat are like fur magnets. It is almost impossible to avoid having one or more cat furs cling to skin, clothing, shoes, bags and more.
John Butler, a researcher and group leader at the National Institute of Standards and Technology, and colleagues agree that cat fur holds tremendous potential in forensic applications.
"An assailant may unknowingly carry clinging cat hairs from a victim's cat away from the scene of a crime, or hair from the perpetrator's cat may be left at the scene," according to Butler and his team. "Either scenario may provide a crucial link and help solve an important case."
Butler's group has already created a DNA test using the STR marker technique. Called the "Meowplex," it, along with the new mtDNA database, provides criminal investigators with additional tools to work with during their cases.
Dog and other animal fur might be added to the larger mix in the future. Other research teams have already analyzed canine mitochondrial DNA.