For the first time, the forensic researchers of Flinders University have examined the presence and transfer of human DNA on pets such as cats and dogs.
This research considers cats both as receptors and vectors for DNA of a person of interest as the key evidence in criminal investigations.
In recent years, DNA analysis technology has become so sophisticated that even the most minute traces of genetic material can be relevant for a crime scene investigation.
Even just brief contact with an object can transfer traces of our genetic material. So called touch DNA isn’t enough on its own to positively identify a suspect, but it can be used to support other lines of evidence, or rule people out.
Touch DNA obtained from a surface doesn’t even require the person to touch that surface, necessarily. In fact it can be transported by a number of means, in skin cells or hairs that drift from a passing body.
The new study is the first to examine how household pets can contribute to DNA transfer, so there’s a lot more work to be done.
But it represents a positive step towards the future collection of more comprehensive forensic evidence which, obviously, would be really helpful in police investigations.
In collaboration with the Victoria Police Forensic Services Department, forensic science researchers Heidi Monkman and Dr. Mariya Goray, from the College of Science and Engineering at Flinders, collected human DNA from 20 pet cats from multiple households.
At the homes of the study participants, the researchers swabbed the fur on the right side of each cat twice, and collected DNA samples from most of the human study participants (one was a minor child who was not sampled). The cat swabs and the human DNA samples were then processed.
In addition, the occupants of the household filled out questionnaires on 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% of the samples and interpretable profiles that could be linked to a person of interest were generated in 70% of the cats tested.
Possible sources could include direct transport of the DNA from a human, such as by patting, or by the cat brushing against a contaminated surface. The DNA could also have been lingering since the last time the cat had contact with a visitor.
However, the mode of transfer of this DNA to the cat, and its persistence on them, is unknown.
An experienced crime scene investigator Dr. Goray, an expert in DNA transfer, says this data can be very relevant when interpreting forensic DNA results obtained from a crime scene that includes pets.
Monkman said, “Collection of human DNA needs to become very important in crime scene investigations, but there is a lack of data on companion animals such as cats and dogs in their relationship to human DNA transfer. These companion animals can be highly relevant in assessing the presence and activities of the inhabitants of the household, or any recent visitors to the scene”.
They said, “Further research is required on the transfer, persistence and prevalence of human DNA to and from cats and other pet animals and the influences animal behavioral habits, the DNA shedder status of the owners and many other relevant factors“.
The article, “Is There Human DNA on Cats?,” has been published in Forensic Science International: Genetic Supplement Series.