Cats may harbor crime scene DNA, scientists say: ScienceAlert

Have you ever had the feeling that your cat might know a little more than he’s letting on? Well, maybe you’re onto something. New research suggests that our little feline friends can be surprising sources of evidence when a crime has been committed.

In particular, a cat’s fur may contain enough DNA shed by a person who has been nearby to serve as evidence of a fleeting encounter between the two. This could mean that while cats cannot be interrogated, they can still help identify criminals.

The new study is the first to examine how pets may contribute to DNA transmission, so there’s a lot more work to be done. But it is a positive step towards the future collection of more extensive forensic evidence – which would of course be very useful for police investigations.

“Collecting human DNA should become very important in crime scene research, but there is a lack of data on companion animals such as cats and dogs in their relationship to human DNA transmission,” says forensic scientist Heidi Monkman from Flinders University in Australia.

“These companion animals can be very relevant in assessing the presence and activities of the household residents, or recent visitors to the scene.”

In recent years, DNA analysis technology has become so advanced that even the tiniest traces of genetic material can be relevant to crime scene research. And we messy people leave our DNA everywhere. Even just brief contact with an object can transfer traces of our genetic material. so-called touch DNA is not enough by itself to positively identify a suspect, but it can be used to support other lines of evidence, or exclude people.

Touch DNA obtained from a surface does not even require the person to touch that surface. It can be transported in various ways, for example in skin cells or hair that drifts from a passing body. Where pets can play a role.

So Monkman and her Flinders University colleague Mariya Goray, an experienced crime scene investigator, teamed up with forensic scientist Roland van Oorschot of the Victoria Police Forensic Services Department in Australia to see if they could extract traces of legible human DNA from domestic cats. .

Their study was conducted on 20 cats from 15 households. In the homes of study participants, the researchers took off the fur on each cat’s right side twice and collected DNA samples from most of the human study participants (one was a minor child who was not sampled). The swabs from the cat and the human DNA samples were then processed.

In addition, the residents of the household completed questionnaires about the cats’ daily behavior and habits. This included how often the cat was touched and by whom in the household.

Detectable levels of DNA were found in 80 percent of cat swabs. For all cats, there was no significant difference between the amount of DNA present and the time since last contact with a human, or the length of the cat’s hair.

The team was able to generate DNA profiles of 70 percent of the cats in the study that can be interpreted well enough to be linked to a human. Most of the DNA came from people in the cat’s own household, but only unknown human DNA was found in six of the cats.

Two of those cats spent a lot of time in the bed of the child whose DNA had not been sampled, which could explain some of the “mysterious” results. The provenance of the unidentified DNA of the four remaining cats is unknown. None of the households had been visited for at least two days prior to the swabs.

One case was particularly interesting: a household with two cats and two people. One of the cats, a hairless sphynx, carried the DNA of an unknown third human. The other cat, a short-haired ragdoll, did not. Both cats had interacted for a bit with the people in their household.

Possible sources include direct transport of a human’s DNA, such as by petting or brushing the cat against a contaminated surface. The DNA may also have lingered since the cat last interacted with a visitor.

“The mode of transmission of this DNA to the cat, and its persistence, is unknown,” the researchers write.

“Further research is needed on the transfer of human DNA to and from cats, and the persistence of human DNA on cats and what may affect the different levels of DNA found in cats, such as behavioral habits and owner status. .”

Or maybe that’s exactly what the cat wants you to think…

The research was published in Forensic Science International: Genetics Supplement Series.