Dyfed-Powys detectives have revealed how 84 year old Betty Guy of Johnston, Pembrokeshire, was killed at her home in an S4C true crime documentary.

In next week’s episode of ‘Y Ditectif’, presented by actress Mali Harries, detectives explain how they investigated the death of pensioner Betty Guy and reveal details of the covert evidence from the case that proved crucial in the conviction of daughter Penelope John and grandson Barry Rogers for her murder.

Detective Chief Inspector Steve Davies of Dyfed-Powys Police explains how they investigated Barry Rogers’ background and gathered evidence following a witness statement from one of his previous partners. But it was an unusual and challenging case as CI Davies says, “We had no body, no crime scene evidence, and these are the tools you normally depend on as a Senior Investigating Officer.”

But it was the decision to gather covert recordings of the mother and son at John’s home in St Dogmaels which became the breakthrough for the investigation team.

Mali Harries listens to the recording of Rogers and John discussing their arrest, “If we deny it all the way..they have no evidence” Rogers is recorded saying.

“It’s only circumstantial evidence. Hearsay. All this is hearsay. They can’t prove it one way or the other” he adds.

“We gave them the chance to tell the truth after their arrest and they didn’t. But through these recordings we got the truth out there” says Detective Inspector Gareth Roberts.

He explains how specially trained officers listened and analysed around 72 hours of recordings, before the evidence was played to the jury at court. “I now realise that it is very difficult these days to keep secrets as police can use all sorts of methods to get to the truth. This is quite reassuring really”, says presenter Mali Harries.

Penelope John and Barry Rogers were each given a life sentence in February 2018, with a minimum of 11 years in jail. Appeals against their sentence have failed.

But for the Dyfed-Powys murder detectives, their motive still remains unclear.

“They had no excuse to do what they did. And I don’t think we’ll ever know exactly why they did what they did” adds Chief Inspector Steve Davies.

The programme “Y Ditectif - Betty Guy” will be broadcast on Tuesday, the 29th of May on S4C at 9.30pm, with English Subtitles.