Ever feel like your cat might know a little more than she’s letting on? Well, you may be onto something. New research suggests that our little feline friends could be surprising sources of evidence when a crime has been committed.
Specifically, a cat’s fur can retain enough DNA shed by a person who has been in its vicinity to serve as evidence of a fleeting encounter between the two. This could mean that even though the cats cannot be questioned, they could still help identify the perpetrators of the crime.
The new study is the first to examine how household pets may contribute to DNA transfer, so much more work remains to be done. But it represents a positive step towards the future collection of more comprehensive forensic evidence, which would obviously be really useful for police investigations.
“Human DNA collection should become very important in crime scene investigations, but data on companion animals such as cats and dogs as it relates to human DNA transfer is lacking.” 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’s inhabitants or any recent visitors to the scene.”
In recent years, DNA analysis technology has become so sophisticated that even the smallest traces of genetic material can be relevant to crime scene investigations. And we messy humans leave our DNA everywhere. Even brief contact with an object can transfer traces of our genetic material. so-called touch the dna is not sufficient on its own to positively identify a suspect, but can be used to support other lines of evidence, or dismiss people.
Tactile DNA obtained from a surface doesn’t even require the person to touch that surface, necessarily. It can be transported by various means, for example, on skin cells or hair moving from a passing body. Which is where domestic pets can play a role.
So Monkman and his 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 human-readable DNA from domestic cats.
Their study was conducted on 20 cats from 15 households. At the homes of study participants, the researchers swabbed the fur on the right side of each cat twice and collected DNA samples from most of the study’s human participants (one was a minor child who was not sampled). Cat swabs and human DNA samples were then processed.
In addition, household occupants completed questionnaires about the cats’ behavior and daily 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 the cat swab samples. For all cats, there was no significant difference between the amount of DNA present and the time since last human contact or the length of the cat’s hair.
The team was able to generate DNA profiles of 70 percent of cats in the study that could be interpreted well enough to link him to a human. Most of the DNA came from people in the same household as the cat, but in six of the cats, only unknown human DNA was detected.
Two of those cats spent a lot of time in the bed of the boy whose DNA was not sampled, which could explain some of the “mysterious” results. The provenance of the unidentified DNA from the remaining four cats is unknown. None of the homes had had visitors for at least two days prior to the swabs.
One case was particularly interesting: a household of two cats and two people. One of the cats, a hairless sphynx, carried the DNA of an unknown third human being. The other cat, a short-haired rag doll, did not. Both cats had interacted you too with the humans in your home.
Possible sources could include direct transport of DNA from a human, such as through patting or the cat rubbing against a contaminated surface. The DNA could also have been present from the last time the cat had contact with a visitor.
“The mode of transfer of this DNA to the cat, and its persistence in them, is unknown.” the researchers write.
“More research is required on the transfer of human DNA to and from cats, and the persistence of human DNA in cats and what may influence the variable levels of DNA found in cats, such as behavioral habits and the molting status of the owners”.
Or maybe that’s what the cat wants you to think…
The research has been published in Forensic Science International: Genetics Supplement Series.
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