Crime: it’s a dirty business

Forensic scientists now have a new way to track criminals and terrorists – through the germs they leave behind.

A University of Colorado at Boulder study has shown that it’s possible to track a person through the ‘personal’ bacteria on their hands, left behind on the objects they touch.

“Each one of us leaves a unique trail of bugs behind as we travel through our daily lives,” says lead author Professor Noah Fierer.

“While this project is still in its preliminary stages, we think the technique could eventually become a valuable new item in the toolbox of forensic scientists.”

Using gene-sequencing techniques, the team swabbed bacterial DNA from individual keys on three PCs and matched them up to bacteria on the fingertips of keyboard owners, comparing the results to swabs taken from other keyboards never touched by the subjects.

The bacterial DNA from the keys matched much more closely to bacteria of keyboard owners than to bacterial samples taken from random fingertips and from other keyboards, Fierer said.

The team found that the pattern of bacteria hardly changed, even after two weeks. “That finding was a real surprise to us,” said Fierer. “We didn’t know just how hearty these creatures were.”

The study showed the new technique is about 70 to 90 percent accurate, a percentage that likely will rise as the technology becomes more sophisticated, said Fierer.

More research needs to done on how human bacterial signatures adhere to different surfaces like metal, plastic and glass, said Fierer. But the new technique may be useful for linking objects to users in cases where clear fingerprints cannot be obtained.

Fierer’s a bit concerned that the technique could be used by the authorities to bypass privacy rules.

“While there are legal restrictions on the use of DNA and fingerprints, which are ‘personally-identifying’, there currently are no restrictions on the use of human-associated bacteria to identify individuals,” he said. “This is an issue we think needs to be considered.”