Dutch police have a new weapon at their disposal in the hunt for rapists – a dog which has been trained to sniff out sperm outdoors, RTL Nieuws said on Tuesday afternoon.

The two dogs have been involved in 80 cases and the trial was so successful that four more dogs will be trained to work in places where sexual assaults have taken place, RTL said.

In two cases, the dog’s evidence was instrumental in solving two sex crimes – one of which involved a young girl who was knocked off her bike and raped.

The dogs are able to identify specific sperm up to a week after the incident. This, says RTL, saves on laboratory time because technicians can identify the sperm sample’s dna straight away, rather than test all sorts of different items for potential evidence.

The sperm dogs are part of a team of 120 sniffer dogs, all trained to focus on specific smells, such as drugs or money.

Last year, the police abandoned plans to train up sniffer rats. They were going to be used to detect illegal fireworks, fake cigarettes and human bones but the plan was dropped because they could not be made ‘operational’.