John William Cooper (born 3 September 1944) is a Welsh serial killer and diagnosed psychopath.
On 26 May 2011, Cooper was given a whole life order for the 1985 double murder of siblings Richard and Helen Thomas, and the 1989 double murder of Peter and Gwenda Dixon.
Cooper was also sentenced for the rape of a 16-year-old girl and a sexual assault on a 15-year-old girl, both carried out at gunpoint, in March 1996, in woodland behind the Mount Estate, Milford Haven, Pembrokeshire.Cooper had a history of crime, including 30 robberies and violent assault.
Footage from the TV game show Bullseye, in which he appeared as a contestant in May 1989, was later used as evidence against him, comparing his image with a sketch of a suspect in the Dixons' murder.
Cooper was sentenced to fourteen years in 1998 for robbery and burglary, enabling the police to collect further evidence against him.
He was released from prison in January 2009.
Through a cold case review, and subsequent developments in DNA and forensic science, the police were able to identify Cooper's shotgun as the murder weapon in April 2009.
Cooper was arrested in May 2009 and was convicted in May 2011 for the double murders and sexual assaults and sentenced to a whole life order, which means he will never be released from prison.
In September 2011, he launched an appeal against his convictions.