Paris, July 27: Scientists working for French police have perfected a technique for “bottling” smells at the scene of a crime to identify suspects by the odour they leave behind.
After conducting a two-year-long programme of tests on a method of detection known as “odourology”, they have concluded that smell can be as effective as using fingerprints or DNA samples to link a criminal with a crime.
The French national police force’s scientific and technical unit, based in Lyon, established that trained sniffer dogs could be presented with a crime’s “smell signature”, then successfully match it to the correct suspect in the olfactory equivalent of an identity parade.
A jubilant police official hailed the new study as a breakthrough in crime-fighting. “We now know beyond doubt that wherever a criminal goes they leave behind molecules of odour unique to them, and which a trained dog can recognise,” he said.
“A burglar who jumps out of a building having tiptoed carefully to the window and taken precautions against leaving fingerprints, hair, or anything which would contain DNA, could still be identified because his smell will have been left on anything he touched, even through his clothing or the soles of his shoes.”
French scientists have refined a technique pioneered in eastern European countries, particularly Hungary and Bulgaria, to gather odours from the crime scene.
The smells gathered can come from tiny droplets of sweat or skin-oils.
Forensic investigators leave strips of a special type of tissue paper at the crime scene to absorb smells, which are then sealed inside a sterile jar. Scientists believe they can retain the smell for up to 10 years.
An arrested suspect is told to hold a clean tissue of the same kind for up to 15 minutes, and this and other samples are then presented to a sniffer dog, to be matched — or not — to the odour from the crime.
The scientists found that, in strictly-controlled experiments, sniffer dogs correctly picked out the suspects’ smells from samples collected at the crime scene, and were successful even when the samples bore the odour of more than one person.
In one of the first genuine cases in which police used the new technique, detectives arrested several suspects in connection with a robbery, unsure which was responsible for the crime. According to a report issued by the scientific and technical unit last week, officers were delighted when sniffer dogs identified the odour of one suspect in a sample taken from the getaway vehicle.