Unique Technique in Netherlands : Sergeant Sniffs Out Way to ID Suspects

Police Sgt. Jan de Bruin proudly displays his collection of glass jars, each containing the scent of a robber, a rapist or a killer.

The scents, extracted from objects on the scene of a crime or from human subjects, could help Rotterdam’s police dogs sniff out some of the city’s most dangerous criminals.

In his new “smell bank,” the first of its kind in the West, De Bruin already has about 40 samples that he can preserve for at least three years.

He plans to build the collection to about 300 samples, providing Rotterdam police with a unique addition to their criminal files.

“Everybody has a different smell that a dog can recognize,” said De Bruin, 48, who has devoted the last 12 years to perfecting the science of collecting and storing human odors. He is technical director of Rotterdam’s police dog unit.

Scientists are impressed by De Bruin’s work, which they say could provide vital clues for criminal investigations.

Other Dutch police forces are envious of Rotterdam’s $700,000 smell bank, while canine experts in other European countries and the United States are intrigued by his methods.

When a serious crime, such as a murder or bank robbery, occurs in Rotterdam, De Bruin is called to the scene with his homemade scent-extraction kit.

He wraps any article bearing traces of the criminal’s personal odor in a sterilized cotton cloth and places it in a large plastic ventilation box, equipped with an electric fan.

As air blows through the box, scent molecules from the object evaporate and are absorbed by the cotton.

After 20 minutes, the cloth is transferred to an airtight storage jar, labeled with the date and place of the crime, and stored in a room especially reserved for De Bruin’s collection.

“This sample was taken from the glove of a bank robber,” De Bruin told a reporter, pointing to one of the jars, the sort more commonly used for preserving fruit and vegetables.

Another sample came from a cigarette lighter, carelessly dropped by a murderer as he fled.

“The whole human body is a source of odors. We leave behind scent molecules wherever we go,” De Bruin said, noting that he also gathered odor traces directly from human skin.

When major crime suspects in Rotterdam are arrested, they are photographed and fingerprinted on arrival at a police station. But they also have to provide a scent sample by holding one of De Bruin’s special cloths for five minutes.

In his experiments, dogs have accurately identified people from a scent sample taken three years ago, but De Bruin believes the specimens could last much longer.

“De Bruin’s techniques are quite new and could be very helpful to police,” said chemist Jan Schaefer, an odor specialist at the TNO private research institute in Zeist, who advised De Bruin on his research.

Police have traditionally used trained dogs to help track down or identify criminals, using the scent of an object belonging to the culprit.

Schaefer said, however, that only highly trained dogs can match a human odor to its owner, and even the most skilled animals make mistakes if improperly handled.

He said the most commonly used police identification test, in which a dog selects a culprit from a line-up of suspects, is unreliable because humans under stress emit different body odors.

It was such flaws that spurred De Bruin, who has worked with dogs for more than 30 years, to devise more scientific ways of putting his canine colleagues to work.

Besides creating his smell bank, De Bruin introduced more sophisticated detection tests. Instead of a row of people, he presents the dog with a row of glass jars containing cloth odor samples, taken earlier from participants in the test.