The killing of an Irish woman stabbed to death by her BDSM “master” and described as a “nearly perfect murder” is the focus of a new documentary.

Elaine O’Hara, 36, from Dublin, was killed by Graham Dwyer, 42, a married architect and father of three, in August 2012. Dwyer had a fetish for stabbing women during sex, and is believed to have had a “Master and Slave” relationship with O’Hara before murdering her, The Daily Mail reports.

O’Hara was initially reported missing by her family, who suspected she had taken her own life. In August 2013, her remains were found in the Dublin Mountains by a dog walker. Her belongings were also found in a reservoir after the dry summer resulted in the water dropping from 20 ft to two ft.

In Secrets of a Psychopath, a three-part documentary airing on Saturday, August 24 through Monday, August 26 on CBS Reality, Criminologist John O’Keefe reveals that O’Hara, a teaching assistant who dreamed of being a teacher, told her friends and family about her sex life, which may have been a cry for help.

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He says: “Elaine was quite open about her sex life, her sexuality and BDSM.

“She advised friends she was having an affair with a married man, and it was not a normal affair, and showed them cuts all over her body.

“It seemed almost peculiarly uninhibited about talking about, which I would say played to her vulnerability.”

Journalist Nicola Tarrant says: “Sometime in 2008, she'd had this conversation with her father where she said she was having this affair with a married man.

“And she said something along the lines of he likes to tie me up and masturbate over me or something. I mean her father was shocked.

Tarrant adds: “But part of her mental illness was that she made inappropriate comments and she made things up.

O’Hara had a history of mental illness. She had been admitted to the hospital for depression 14 times, had self-harmed, and had tried to take her own life three times, The Daily Mail reports.

So O’Hara’s comments were dismissed by the family.

However, O’Keefe says: “She described this relationship in quite a normative way as well.

“Elaine was telling her coworkers it's on, it's off, sometimes he contacts me, sometimes he doesn't.

“Whatever was happening, she was clearly not comfortable in this relationship.

“This wasn't just attention seeking, we have to assume that this was perhaps an early cry for help.”

Despite O’Hara’s openness about her lifestyle, her family was still stunned to learn of her “double life” after she disappeared. In her apartment, detectives and family discovered PVC rubber outfits, chains, and a notebook listing websites of extreme BDSM.

Read More: Sadistic Irish killer receives love letters and lingerie from female fans

Tarrant says: “They did wonder had any of this stuff had anything to do with [her disappearance].

“On the laptop were a lot of writings that were very deep into this fetish world. They were also able to find that she was going online and meeting up with people.

“She was almost living a double life. The Elaine that her family knew wasn't the same Elaine that was going online and meeting people for bondage and hard core sex.

In March 2015, Dwyer was convicted by unanimous verdict in the murder of O’Hara.

Elaine O'Hara.Facebook/BreakingNews.ie