Dogs like Ralph, a spaniel, didn't get on very well with his owners because he needs a lot of attention.
"He was bored and he was a bit too lively for them", said a police trainer Ian McParland.
Now he's joined the police force and has started his new life as a sniffer dog.
Every year hundreds of dogs get given to dog homes because they need more looking after than people realise.
This is a chance for these cheeky canines to put their energy to good use.
There's 30 places for new recruits with a good nose. If you think your dog might be happier in a career as a crime fighter, call the Dog Procurement Officer on 020 8649 1626.