Unique bacterial fingerprint can help forensics extract suspect’s DNA, study finds

Criminologists usually say that ‘every contact leaves a trace. This has never been more true. Imagine: you are attacked by someone. You try to defend yourself. There is therefore necessarily contact. Until now, to identify an attacker, investigators needed to find, at least, a few hairs, bodily fluids or pieces of skin to extract the DNA. This is why we often look under the victim’s nails when there has been a fight. But sometimes we don’t find anything at all.

A team of forensic science experts has just shown that each person has a unique bacterial fingerprint. Their research was published in the Nation Library of Medicine, on March 19, 2024. They called it “the Touch Microbiome.” And it turns out that these bacteria are transferred to everything the skin comes into contact with. By analyzing them, we could extract DNA and identify the suspect.

These bacteria stay on objects for more or less time, everything will depend on the porosity of the surface. In the worst case, on glass, for example, they will stay for a little less than a month. On the other hand, on a cotton T-Shirt, researchers showed that traces of DNA could be found for six months. Better still, they discovered that these bacteria could be transferred from one item of clothing to another. This would mean that if an attacker simply rubbed himself or stayed close to his victim long enough, even without touching him, his bacterial fingerprint could be found on the clothing.

To recover this bacterial fingerprint on a glass or on a T-Shirt, simply use a DNA extraction kit. This is what we often see in series when scientific experts pass a sort of cotton swab over an object. We do the same thing on the suspect’s skin. Then we put everything in a machine which will then say if the bacteria match. It is the same principle as the PCR test during the Covid era. A technique which could become a formidable weapon for the scientific police.