Fritzl May Have Planned 'Dungeon' Since 1978, say police

The man accused of keeping his daughter as a sex slave in a windowless Austrian cellar for 24 years may have planned to build the tiny cell where she was held years earlier, police said on Monday.

Josef Fritzl, 73, built an extension to his house at number 40 Ybbsstrasse between 1978 and 1983.

The original house dated back to around 1890. Fritzl received permission to build the extension in 1978.

"We believe that, already in the planning phase, the intention must have been there to build... a secret area, a small dungeon," chief investigator Franz Polzer told a news conference here.

Fritzl, currently in custody, has admitted to police that he imprisoned and sexually abused his daughter Elisabeth, now 42, in a cramped bunker beneath the family home since 1984 when she was 18.

Initially, Elisabeth was held in a single room of 35 square metres (380 square feet), but when she became pregnant from the sexual abuse and gave birth to several children, Fritzl extended the dungeon, breaking through walls into other unused cellar rooms beneath the older part of the house, Polzer explained.

By 1993, the dungeon comprised three rooms measuring a total 55 square metres, the investigator said.

Polzer said they had found an earlier entrance to the dungeon, a half-tonne concrete door, that had clearly been used before the two reinforced steel doors that investigators had initially found.

In all, "if you want to get into the dungeon, you have to go through eight locked doors" and electronic combinations were needed to open the last three, he said.

The lawyer of Josef Fritzl, the Austrian man accused of keeping his daughter captive for 24 years and fathering seven of her children, says his client has a severe mental disorder and that he is preparing an insanity defence for him.

"I believe that the trigger was a mental disorder, because I can't imagine that someone has sex with his own daughter without having a mental disorder," Rudolf Mayer said about his client in an interview.

He said anyone with that kind of psychological illness "didn't choose" to do what police allege he did.

Mayer said if experts determine Fritzl can be considered certifiably insane, and if he is convicted, he would go to a psychiatric institution rather than a prison.