Cats carry traces of human DNA that help solve crimes

A recent study found that cats could be unexpected sources of key clues at a crime scene, given their role in passing on human DNA.

In particular, cat fur could retain enough DNA from a person who was nearby to serve as evidence of a fleeting meeting between them.

This could mean that while cats cannot be interrogated, they can still help identify criminals.

This new study, led by forensic scientists at Flinders University, is the first of its kind to investigate how pets facilitate DNA transfer, so there is still a lot of work to be done. But it represents a positive step towards the future collection of more complete forensic evidence, which will obviously be really useful in police investigations.

“Collecting human DNA should become extremely important in a crime scene investigation, but data on companion animals such as cats and dogs is not enough in relation to the transfer of human DNA,” says forensic scientist Heidi Monkman from Flinders University in Australia. important in assessing the presence and activities of the family or any recent visitor to the scene.”

In recent years, DNA analysis technology has become so advanced that even the smallest trace of genetic material can be relevant to a crime scene investigation.

We messy people leave our DNA everywhere. Even brief contact with anything can transfer traces of our genetic material. So-called tactile DNA alone is not enough to positively identify a suspect, but it can be used to confirm other lines of evidence or to rule people out of a crime.

Touching DNA obtained from a surface does not necessarily require the person to touch that surface. It can be transmitted in various ways, such as through skin cells or hair swept from a passing object. This is where pets can play a role.

So Monkman and her Flinders University colleague Maria Jurai, an experienced crime scene investigator, teamed up with forensic pathologist Roland van Orhot of the Victorian Police Forensic Service in Australia to see if they could extract human-readable DNA traces from domestic cats.

The study was conducted on 20 cats from 15 families. At the homes of the study participants, the researchers double-scanned the fur on the right side of each cat and collected DNA samples from most of the study participants (one of whom was an unsampled juvenile). Cat swabs and human DNA samples were then processed.

In addition, residents of the house filled out questionnaires about the daily behavior and habits of cats. This included the amount of touching the cat and anyone else in the house.

Detectable levels of DNA were found in 80% of feline swab samples. For all cats, there was no significant difference between the amount of DNA present, the time since last human contact, or the length of the cat’s coat.

The team was able to create DNA profiles for 70 percent of the cats in the study that could be interpreted well enough to be linked to humans.

Most of the DNA was from people in the same cat family, but only six cats were found to have unknown human DNA.

The two cats spent a lot of time in the crib for which no DNA samples were taken, which may explain some of the “fuzzy” results. While the DNA source of the remaining four cats remained unidentified, none of the families received visitors for at least two days prior to sampling.

One particularly interesting case is a family of two cats and two people, in which one of the cats, a pharaoh cat (which has no fur), carried the DNA of an unknown third person. The other cat, a short-haired ragdoll, did not. And both cats interacted in the same way with people in the house.

Possible sources of direct transmission of DNA from humans could include, for example, cats cleaning contaminated surfaces. The DNA may also have been preserved from the cat’s last visit.

The authors write: “The manner in which this DNA is transferred to and stored in the cat is unknown. Further research is needed on the transfer of human DNA from cats and the retention of human DNA in cats, which may affect various levels of DNA present in cats, such as behavioral habits.

The results of the study are published in the journal Forensic Science International: Genetics Supplement Series.