AMSTETTEN, Austria - The Austrian man who allegedly imprisoned his daughter and fathered seven children with her first planned to build his secret cell as early as 1978, when she was just 12, authorities said Monday.
Investigators said a total of eight doors fitted with sophisticated locks and electronics secured the underground warren of windowless rooms where they say Josef Fritzl held his daughter captive for two dozen years.
"This was not built from one day to the next," said police Col. Franz Polzer, who is overseeing the investigation into a case that has stunned Austria and the world.
He said the main door weighed about 500 kilograms.
Polzer said an investigation showed that the apartment complex owned by Fritzl originally was built in 1890, and that he applied for permits to expand it in 1978. He said police believe the plans for that expansion included the secret rooms because adding them later would have been far more difficult and expensive.
Prosecutors told reporters in Amstetten, Fritzl's hometown about 120 kilometres west of Vienna, that they will have their first meeting with the 73-year-old suspect on Wednesday or Thursday.
Officials said Fritzl's wife, the daughter he allegedly imprisoned and raped, and the children born of the illicit relationship are learning how to live together as they get psychiatric care and counselling.
They said the children were given a fish tank at the clinic, and the youngest - a five-year-old boy - received a teddy bear.
Fritzl's lawyer, meanwhile, indicated he is preparing an insanity defence.
In an interview broadcast late Sunday, lawyer Rudolf Mayer said he believes Fritzl has a serious mental disorder and that anyone with that kind of psychological illness "didn't choose" to do what police allege he did.
Mayer said experts will have to determine Fritzl's mental state and decide whether the suspect can be considered certifiably insane. If that is the case, and Fritzl is convicted, he would be confined to a psychiatric institution rather than a prison, he said.
Investigators have said Fritzl confessed last week that he held his daughter captive in a windowless cell, fathered her seven children, and tossed the body of one who died in infancy into a furnace.
"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," Mayer said.
Fritzl has not yet been charged, but remains in pretrial detention. Police reiterated Monday they have no evidence that the retired electrician had an accomplice.
Authorities first began to unravel the complex story April 19, when a 19-year-old girl who Fritzl fathered with his daughter, Elisabeth, was admitted to a hospital suffering from an unidentified infection.
Doctors, unable to find any medical records for the girl, appealed on television for her mother to come forward. Fritzl then accompanied Elisabeth to the hospital on April 26 and opened up to police.
The 19-year-old remained in hospital Monday in critical but stable condition, although clinic spokesman Klaus Schwertner said her situation "has stabilized somewhat in recent days."
Investigators have said they believe Fritzl concealed his crimes from his wife, Rosemarie, and her sister said Rosemarie believed her husband's cover story that Elisabeth had run away from home to join a cult.
"We were all taken in by him," the sister, who gave her name only as Christine R., said in an exclusive television interview with The Associated Press. "Every person that looked in his eyes was fooled by him."
Christine R. described Fritzl as a "tyrant" who instilled a culture of fear at home, which may have explained why his wife and other children apparently never dared venture into the cellar - which Fritzl warned was strictly off-limits.
"When he said it was black, it was black, even when it was 10 times white," said the woman, who was interviewed Saturday at her home in Austria. "He tolerated no dissent."
"Listen, if I myself was scared of him at a family party, and I did not feel confident to say anything in any form that could possibly offend him, then you can imagine how it must have been for a woman who spent so many years with him," she said.
She also said her imprisoned niece - now 42 - ran away from home as a 17-year-old, about six months before police say she was locked into the secret basement rooms. The previous attempt to flee may have made her father's story that the girl joined a cult more believable.
She also said Fritzl was jailed for "a year and half" on what she said was a 1967 rape conviction, but said she could not offer details.
On Saturday, the Oberoesterreichische Nachrichten daily printed an excerpt of what it said was a 1967 court record found in the state archives in Linz, in which a Josef F. was accused of breaking into the apartment of a 24-year-old nurse and raping her.
Police have declined comment, saying records that old would have been erased under Austria's statutes of limitation. But authorities are awaiting old court records that the media say document the case.