Josef Fritzl, the Austrian builder who locked his daughter in a cellar and fathered seven children with her, sees himself as a born rapist, a victim of his own tyrannical mother.

According to the first leaked account of interviews with a forensic psychiatrist, which is due to appear in two Austrian newspapers today, Fritzl hatched his plan to incarcerate his daughter, Elisabeth, while he was in prison for rape.

“I have realized that I had a mean streak. For someone who was born to be a rapist, I have managed to contain myself for a relatively long period,” Fritzl is quoted as telling the psychiatrist in a 130-page report leaked to the tabloid newspapers Kronen Zeitung and Österreich.

Fritzl, 73, is awaiting trial for sexually abusing and incarcerating Elisabeth, 42, in a purpose-built dungeon beneath his house in the town of Amstetten. He fathered seven children by her, one of whom died shortly after birth and Fritzl burnt his body in an oven.

Three of the surviving children were allowed to live upstairs with him and wife, Rosemarie, 69, while their three siblings were condemned to a shadowy existence with their mother in the cellar. They never saw daylight until they were freed by police on April 26. It emerged that Fritzl had a previous criminal record for sexual offences.

In 1967 he was sentenced to 18 months in prison for brutally raping a 24-year-old woman at knifepoint in her home.

According to the report compiled by Dr. Adelheid Kastner, a prominent forensic psychiatrist who conducted in depth interviews with the builder, Fritzl found the “ideal solution” to his deranged fantasies after he was released from prison. It was then that he decided to lock up his daughter in the cellar so that he could “live out” his “evil side” while leading a seemingly normal life in the flat upstairs.

Fritzl told the psychiatrist that his relationship to women was shaped by his experience with his abusive mother, who allegedly beat him and isolated him from other children until he started school. He was an “alibi child,” Fritzl told the psychiatrist – his mother only had him to prove to her partner that she was not sterile.

Dr. Kastner came to the conclusion when she was dissecting the personality of Fritzl that the builder managed to distance himself from what he was doing by never looking his victim in the face when he raped her.

“He was not only incredibly able to lead a double life but also managed to maintain a triple life without any problems,” Dr. Kastner wrote, indicating that Fritzl played down the gravity of his crimes in his mind.

“Mr. Fritzl resembles a volcano; under the surface that appears almost banal there is an evil streak. He is torn apart by his desires that he cannot master,” Dr. Kastner wrote.

The report declared Fritzl clinically sane and fit for trial, but also diagnosed a “severe combined personality disorder and a sexual disorder”.

“It is to be expected that Mr. Fritzl would perpetrate deeds with severe consequences also in the future,” Dr. Kastner concluded.

On the basis of her report the prosecution has demanded from the court that Fritzl be tried and sentenced, then committed to an institution for the criminally insane, where he would receive psychiatric care and therapy including, if deemed necessary, medication.

The trial is expected to start early next year.