Twisted Minds podcast: Child killer Derek Percy’s sick Barwon prison taunts over who he murdered

Dr Karen Owen has interviewed thousands of sex offenders, but Derek Percy stands out as the most puzzling. Listen to our Twisted Minds podcast.

It had become a monthly ritual.

Dr Karen Owen would trundle down the Barwon prison corridors to the cell of convicted child killer Derek Percy.

The white-haired old man would look at her.

She’d ask him, yet again, if he would partake in the treatment programs she ran for sex offenders.

He would grunt his response. ‘No’. And again, she’d retreat, defeated.

“I interviewed him a number of times over the years for that purpose. But he was a frustrating man from a treatment provider’s point of view, because he had very early on disclosed some things to a psychologist way before I even entered the system and that information was used against him in a legal sense, and so he shut down,” Dr Owen tells the Twisted Minds podcast.

“He decided that he was going to keep all of his secrets to himself, and he took them to his grave.”

Dr Karen Owen has worked at almost every prison across Victoria and has sat down with hundreds of sex offenders. Picture: Alex Coppel

In 1970, Percy was remanded indefinitely for the murder of 12-year-old Melbourne girl Yvonne Tuohy.

He was deemed criminally insane and repeatedly said he could not remember if he had committed more murders.

However, he has been linked to some of Australia’s most notorious cold cases including the case of seven-year-old Linda Stilwell, who went missing near Melbourne’s Luna Park in 1968.

Then there’s the Wanda Beach murders of Christine Sharrock and Marianne Schmidt in 1965, the abduction and murder of three-year-old Simon Brook from his frontyard in Glebe, Sydney, in 1968, the murder of six-year-old Canberra boy, Allen Redston and the infamous case of the three Beaumont Children, who disappeared from Somerton Park, Adelaide, in 1966.

“Particularly towards the end of his life, when he was quite ill, the police reinterviewed him, and every time we went down to see him, there was that hope that there might be some change, or that he was reflecting on his life and maybe want to give up some of the information that we all very strongly believed that he held,” Dr Owen, a forensic psychologist with four decades’ experience working in mental health, said.

Derek Percy, as he appeared in a police mugshot not long after his arrest. Picture: Supplied

Convicted murderer Derek Percy in 2007.

She wasn’t alone in her frustration. Almost every qualified mental health practitioner in the state had attempted to crack Percy but none could establish what had caused his offending.

Esteemed forensic psychologist Professor James Ogloff, who appeared in Episode Two of Twisted Minds, spent hours with Percy, a man he describes as a “model prisoner” but bizarrely “non-emotive”.

“He’s someone who has no real interest in relationships and people,” Prof Ogloff said.

Linda Stilwell, 7, went missing from the St Kilda foreshore in August 1968.

Yvonne Tuohy, 12, was murdered in Warneet by Percy in 1969.

In most cases, practitioners are able to identify what has triggered an individual’s offending, and there are established “pathways to offending” that most criminals will follow.

For example, flashing or stealing underwear are often the gateway crimes to more serious sexual offences such as rape.

Dr James Ogloff is one of Australia’s leading experts on stalking. Picture: Alex Coppel

As Australia’s leading expert in sex offender treatment, Dr Owen is credited with helping introduce rehabilitation programs to prisons in the 1990s.

Prior to this point, sex offenders simply went to prison, did their time, and were released to reoffend again without any treatment that could hope to curb their behaviour.

She’s interviewed thousands of sex offenders, but Percy stands out as the most puzzling.

“He was very rare because there was no reasonable explanation as to what commenced his offence pathway,” she said.

Professor Ogloff concurs.

“We often look to people’s lives growing up, but his life was almost ideal, growing up in the 40s and 50s in Australia, with the normal mum and dad, family holidays, those sorts of things. He was a very smart person but he was always socially isolated, a loner, and from a very young age had developed these very, very strong deviant sexual fantasies.”

Originally published as Twisted Minds podcast: Child killer Derek Percy’s sick Barwon prison taunts over who he murdered