Incest father built prison

Austrian police investigating Josef Fritzl's imprisonment of his own daughter say she was just a youngster when he first planned to convert the basement of the family home into a prison cell where he held her captive for almost a quarter of a century.

SOUNDBITE: Franz Polzer, head of criminal investigation unit, saying (German):

"We are certain that he had for a long time been planning to integrate an area, hidden from the authorities, within this construction, a small area, a small secret, a bunker."

Fritzl is under investigation for a string of alleged offences relating to his imprisonment, the sexual abuse of his daughter and the seven children he had with her.

He's also at the centre of renewed inquries into an unrelated unsolved murder.

But Fritzl's lawyers say he's a broken man and psychiatric tests are due to be carried out.

SOUNDBITE: Rudolph Mayer, Josef Fritzl's defence lawyer, saying (German):

"We have to examine in what way he is mentally disturbed, and I think he has to be insane or he would not have been able to perpetrate such acts. We have to examine whether he was so disturbed that he didn't know what he was doing and therefore can't be held responsible for his actions."

Investigators are examining the cellar where Elisabeth Fritzl was held to see if her father would have carried out his threats to gas her and the children if they tried to escape.

Paul Chapman, Reuters