It was 1989 and police detectives in Pembrokeshire in southwest Wales suspected they had a serial killer on their hands.
Holidaymakers Peter and Gwenda Dixon had been shot dead while out for a walk together on a costal path. Peter Dixon had been robbed, and his wife sexually assaulted, as reported by Wales Online.
The crime bore a striking resemblance to another committed four years earlier.
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Richard Thomas and his sister Helen Thomas had been found shot dead in the burned out wreckage of their farmhouse, as reported by The Guardian.
Officers felt sure the murders were linked – the work of a serial killer – but despite a large-scale manhunt, no arrests were made.
Then, in 2009, a cold case team picked up the file.
Speaking in an ITV documentary, The Gameshow Serial Killer: Police Tapes, Detective Inspector Louise Harries said: “We obviously wanted a result because you had horrendous offences that had happened, and there were the victim’s families out there, who were still all these years later looking for answers, so you have that feeling of burden that you want to get justice for those families.”
Quickly, the officers noticed the similarities between the killings and the modus operandi of a local burglar by the name of John Cooper. There was even an artist’s impression of the alleged killer in the file that looked rather like him.
They brought Cooper in for an interview, but got nowhere.
Then, they had a breakthrough.
They discovered Cooper had appeared on an episode of the popular TV gameshow Bullseye back in 1989, exactly a month before the Dixon murders. They figured that by watching the episode, they would have a much clearer idea of what Cooper looked like at the time of the killings and could see if it matched up with the artist’s impression.