Science News

'Smell of death' could help sniffer dogs

Forensic toxicologists have pinpointed the specific chemical compounds emitted by decaying human bodies in an effort to improve police sniffer dogs’ ability to find buried bodies, vastly reducing the number of so-called ‘false positive’ results.

University of Leuven PhD student Elien Rosier conducted the research at the institution’s campus, outside Brussels.

Currently experts train cadaver dogs by exposing them to rotten pig flesh, because of its similarity to decaying human tissue. Pig and human flesh share the same microbes found in the gut, while the hair and body fat ratio are similar.

“We sampled the remains during six months of decomposition and we could identify 452 different compounds,” said Rosier. “From all those compounds we searched for human specific compounds using principal component analysis and we could identify a combination of eight compounds that were specific for human and pig remains.”

Rosier placed organs and tissue samples from human corpses previously used in autopsies into a jar. As they were not airtight, the screw caps enabled air to get inside. RosNier then regularly gathered samples of the gases that formed over time and exposed them to police sniffer dogs. Her research team did the same for tissue and organ samples of pigs, mice, rabbits, frogs and birds.

Until the six-month Leuven study, human and pig flesh had not been studied under the microscope subject to the same conditions.

By discovering a handful of compounds only found in pigs, Rosier believes sniffer dogs can be better trained to only seek out human tissue when sent to potential crime scenes.

“When they are training cadaver dogs now they can use chemical products, but those compounds that are used in those chemical products are not specific for humans, so it is possible that a dog, a cadaver dog, gives a positive signal on a pig or a dog or a cat that people just buried outdoors,” she added.

The study was the result of a request by federal police to the university’s toxicology department, led by Professor Jan Tytgat, to find a specific human marker that could help improve sniffer dogs’ training.

According to forensic toxicologist Eva Cuypers, who supervised the study, “we made this cocktail here in the lab and we took them to the canine team of the federal police and so we tested if the dogs reacted to this mixture of compounds and actually they did. So they recognized the mixtures as being human decomposing material.”

In some media reports, US-based researchers said the research was flawed, suggesting that isolated tissue subjects might only form part of the complex smell of compounds that develop in whole decaying bodies.

Rosier answers that criticism by stating that the same compounds released in her laboratory would also be released in a full body.

Cuypers says that the team’s next task will be testing their research outdoors with buried bodies, which should help them silence any critics.

“In the lab it was only just parts of animals and human beings and it will be very important to explore what happens when we do the full body. It will be very interesting in order to go much closer to the actual problem on the field that the cadaver dogs experience,” said Cuypers.

Tytgat said that in addition to training cadaver dogs “much, much better”, it will also be possible to develop a portable device in future. “It’s definitely possible, and then such a device can be used as a sniffing dog, an instrumental sniffing dog,” he said.

As well as helping police find murder victims, Tytgat said the research could be useful in finding bodies after mass disasters, such as earthquakes and tsunamis.