A 50-year-old double murder mystery involving siblings Griff and Martha Thomas, found dead in their Pembrokeshire farmhouse in December 1976, is being re-examined after police conducted a fresh forensic review. The case has been linked to notorious serial killer John Cooper, known as the 'Bullseye' killer.
The siblings, aged 73 and 70 respectively, were discovered at their isolated Ffynon Samson farmhouse by a postman who raised the alarm. Inside, Martha Thomas was found with severe head injuries, while her brother Griff's body was burned. The scene was described as a "bloodbath" by a family member.
An initial police investigation concluded, in January 1977, that Griff had likely killed his sister before starting a fire and dying himself. An inquest later ruled Martha was "unlawfully killed" by her brother. However, the family and friends of the siblings never accepted this theory, believing both were murdered.
Suspicion later fell on John Cooper, who lived in the Milford Haven area and was responsible for a series of murders and rapes in South Wales during the 1980s and 1990s. His crimes bore similarities to the Thomas case, including the setting of a victim's home on fire. Cooper was arrested in 2009, years after his appearance on the 1980s game show "Bullseye" led to his moniker. He was convicted in 2011 and given a whole-life sentence.
Forensic psychologist Dr. Clive Sims supported the theory that Cooper was responsible for the 1976 deaths, calling the original inquest verdicts "unsafe." Sims suggested the deaths may have resulted from a "botched burglary," pointing to an empty cash box and broken-into bureau at the farmhouse. He noted that Cooper had a history of taking bank cards and jewelry during crimes, and that it would be unusual for someone to begin a criminal career of such violence late in life.
However, others have expressed doubt. Steve Wilkins, former senior investigating officer in the John Cooper inquiry, noted differences in modus operandi between Cooper's known crimes and the Thomas murders. He highlighted that thousands of pounds in cash were left at the farmhouse, which would contradict Cooper's typical motive of financial gain.
Dyfed-Powys Police reopened the cold case in October 2022, utilizing new forensic technologies to re-examine evidence such as fingerprints, DNA, and blood-group information. This review included Martha Thomas's diaries, original investigation documents, and postmortem molds. Despite extensive work, police have been unable to definitively solve the case.
The investigation is now being handed over to HM Coroner, who will provide guidance on how to proceed. It remains uncertain whether the case will be reactivated as an active investigation or if new inquest proceedings will be considered. The family of Griff and Martha Thomas has been kept informed of the progress made during the review.