The latest species to join Dutch police is hard at work behind the
blacked-out windows of a building in Rotterdam: rats learning to
sniff out crime and a new forensic future.
Derrick, Thomson and Thompson, Magnum and Poirot, all named after
fictional detectives, are being groomed to help police not only
keep the streets clean but also save time and money.
"As far as we know we're the first in the world to train rats to be
used in police investigations," said Mark Wiebes, who heads the
Dutch police "innovation" centre.
Each rat costs just 10 euros (around $13) and can, in theory, be
taught to identify any odour, from drugs to gunpowder, while a
sniffer dog costs tens of thousands of euros to buy and train.
A police dog's training also takes around eight months, although
once completed the dog's abilities are far greater than a
rat's.
The rats have been living in a cage inside a small prefab building
since late 2011, alongside more grandiose buildings and grounds
where police dogs and horses are trained.
The rats learn quickly in the darkness the nocturnal rodents
prefer.
"They need barely 10 to 15 days to learn to distinguish a certain
smell," the policewoman in charge of the project, Monique
Hamerslag, told AFP, lifting Derrick out of his large cage and into
a smaller one where he will be put to work.
"The more boring a rat's life is, the better" it is at detective
work, said Hamerslag, who also discovered that male rats are better
at the job than female rats.
Rather shy animals
Four small metal tea diffusers are tied to the side of the cage,
one of which contains gunpowder traces. It takes Derrick, a largish
brown-black rat, two seconds to point it out with his whiskered
snout.
He is rewarded with a 'click' sound and a sunflower seed to nibble
on.
Detecting gunpowder traces is a particularly useful ability to have
when there are several suspects after a shooting.
Each laboratory test to identify traces of gunpowder is expensive
and takes up to two hours, more for multiple suspects.
And while getting fingered by a rat cannot be used in court, it
gives forensics a clue as to which clothing they should test
first.
Dutch police can only hold someone without evidence for a few
hours, so the rats can help prevent a guilty suspect being
released.
Hamerslag developed the idea in her thesis while studying to join
the police, drawing inspiration from an aid group that used rats to
sniff out anti-personnel mines in Tanzania.
Tests on the rat detectives' viability are promising. Wiebes hopes
they can start sniffing out real crime by early next year, although
he admits that date may be "optimistic".
The major problem with rats is their shyness. They are reluctant to
be placed in new situations, such as crime scenes where they might
be called upon to find a body in a strange building or drugs in a
shipping container.
"It's best to bring the smell to the rats and not the other way
round," said Hamerslag. "That means we have to take samples and
bring them to where the rats live."
Police rats will never replace police dogs, she said, but they have
different and complimentary skill sets.
"A dog is a natural predator, and so is not afraid to explore an
unfamiliar place," said Wiebes.
"On the other hand a dog couldn't live like a rat, spending their
whole time in a small enclosed space, he'd get bored."