Can we catch criminals by smell?

Move over sniffer dogs, people who witness a crime may be able to identify criminals by their body odour, suggests new research.

Nose-witnesses can be just as reliable as eye-witnesses, the findings showed.

"Police often use human eye-witnesses, and even ear-witnesses, in lineups, but to date there have not been any human nose-witnesses," explained Professor Mats Olsson, experimental psychologist at the Karolinska Institutet in Sweden.

"We wanted to see if humans can identify criminals by their body odour," Olsson noted.

Dogs have been used to identify criminals through body odour-identification in court, but it is commonly thought that the human sense of smell is inferior to that of other mammals.

To find out more about human odour memory following stressful events, Olsson and his team investigated how well we identify body odour in a forensic setup.

In their first experiment, participants watched video clips of people committing violent crimes, accompanied by a body odour that they were told belonged to the perpetrator.

They also watched neutral videos, with a similar setup. Then they identified the criminal's body odour from a lineup of five different men's odours, showing correct identification in almost 70 per cent of cases.

"It worked beyond my expectation," Olsson explained.

In another test, the team conducted the same experiment but varied the lineup size -- three, five and eight body odours -- and the time between observing the videos and undertaking the lineup -- 15 minutes up to one week.

In lineups of up to eight body odours, participants were still able to distinguish the criminal.

The accuracy of their identification did reduce with the larger lineup size, which is in line with studies on eye and ear-witnesses.

The results also showed that the ability to distinguish the criminal's body odour is significantly impaired if the lineup is conducted after one week of having smelt the offender's body odour.

The findings appeared in the journal Frontiers in Psychology.

"Our work shows that we can distinguish a culprit's body odour with some certainty," Olsson said.

"This could be useful in criminal cases where the victim was in close contact with the assailant but did not see them and so cannot visually identify them," he noted.

--IANS

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