Britain’s only sperm-sniffing dog, Billie, a cocker spaniel is retiring after six years in the role as reported by The Times (the BBC reported that he started in March 2016 which means he worked for just over 4 years). He was trained to detect seminal fluid. He worked for Derbyshire Constabulary where he helped to investigate rape and sex assault cases over the past six years. Sperm-sniffing dogs are particularly useful where ultraviolet light detection is less effective. Apparently he was unique in the UK but not in the world.

Billie a seminal fluid sniffing dog. Photo: Derbyshire Police.
A Newsweek report of May 2018 reported on Dutch police dogs trained to sniff out seminal fluid. It remains a very successful program which commenced in 2015. At the time it involved five dogs in Rotterdam and Amsterdam and in the East of the Netherlands. The report also said that sperm-sniffing dogs had been trained in Sweden and Norway. Dutch dogs were the first to be trained according to this report.
These dogs can be trained to detect tiny amounts of evidence as small as 0.05 mL. As mentioned, they are particularly useful in outdoor spaces where ultraviolet light to detect semen is less effective and it only works best in the dark.
Billie completed 18 searches from the time he was first deployed in March 2016 at Derbyshire Police until September. He was considered an asset by superintendent Dick Hargreaves at Derbyshire Police.
He was trained to detect seminal fluid on surfaces where it had remained for more than a year. He worked successfully on numerous occasions. Other dogs and other police forces have been trained to detect seminal fluid alongside other substances such as blood.