John Cooper 'link' to 1976 Pembrokeshire farm deaths
A forensic psychologist believes multiple killer John Cooper could be linked to the deaths of an elderly brother and sister from Pembrokeshire.
Dr Clive Sims questions the verdicts reached at inquest into the deaths of Griff and Patti Thomas at their farmhouse in Llangolman in 1976.
Cooper was jailed in May for the murders of Richard and Helen Thomas and Peter and Gwenda Dixon in the 1980s.
Dr Sims told BBC Wales's Taro Naw there are similarities between the crimes.
Speaking on the current affairs programme, which returns to S4C on Monday, he calls for the investigation into the 1976 deaths to be reopened.
After reviewing the evidence before an inquest jury, he thinks the verdicts reached were "unsafe".
Griff and Patti Thomas, aged 73 and 70, were found dead in December 1976.
Although Dyfed-Powys Police initially launched a double murder investigation, within a few weeks they concluded Mr Thomas had argued with the sister he had lived with for 70 years, before hitting her on the head with a blunt instrument, and setting himself on fire.
Despite an extensive search, no weapon was ever found.
In February 1977 an inquest returned a verdict of manslaughter in the case of Miss Thomas and an open verdict for her brother.
Dr Sims said: "I feel that there would be substantial evidence for looking at this case again as a cold case."
He believes that the brother and sister were killed by an intruder following a "botched burglary".
"There is an empty cash box, the bureau has been broken into, the back door is unlocked and certain aspects of it simply do not make sense," he said.
Cooper was jailed for life after a jury at Swansea Crown Court convicted the 66-year-old of the 1985 murder of brother and sister Richard and Helen Thomas, and Oxfordshire couple Peter and Gwenda Dixon in 1989.
The Thomases were executed at their remote farm house near Milford Haven during what the jury heard was a botched robbery.
The Dixons from Oxfordshire were killed while on holiday walking the Pembrokeshire coastal path. Their bank cards and jewellery were stolen.
Dr Sims, an experienced profiler, who assisted in profiling the murderer of five women in Ipswich in 2006, said: "There are enough similarities between the crimes to suggest that he may at least be a suspect in this case."
Although Cooper had no record of criminal activity at the time of the deaths at Llangolman in 1976, Dr Sims thinks it is likely that he was responsible for other serious crimes long before he killed the Thomases at Scoveston Park in 1985.
Cooper was 40 at that time.
"It's quite probable that he would have been offending earlier," said Dr Sims.
"It would be extremely unusual for someone to start that late in life on a criminal career, and to start with that level of violence," says Dr Sims.
Following Copper's conviction in May, Dyfed-Powys Police said officers were reviewing whether he was connected to any other murders.
Cooper has been linked with the death of Florence Evans, known as Flo, who was found fully clothed in the bath of her home in Rosemarket shortly after the Dixons were shot.
Detectives are also looking at any "connectivity" with the deaths of Harry and Megan Tooze who were shot at close range at their farmhouse at Llanharry near Bridgend in 1993.
Taro Naw is broadcast on Monday, 12 September, on S4C at 21:30 BST.