Josef Fritzl: The absolute ruler of his underground concrete hell

In the dock, dressed in a grey dog's-tooth jacket, charcoal trousers, blue shirt and striped tie, sat Josef Fritzl, her father and former jailer who turned the basement of the family home in Amstetten into a circle of hell, or as the prosecutor described it "a hidden concrete kingdom".

Testifying in a pre-recorded video interview, which will be divided into two-hour blocks to spare the jury its cumulative horror, Ms Fritzl's exact words will not be revealed to the public or press in a bid to preserve what is left of her shattered privacy.

Yet the full horror of her long ordeal was laid out yesterday by Christiane Burkheiser, the prosecutor: "He would come, switch the lights off, rape her, leave. Lights off. Rape. Lights on … He used her like a toy. He came, he took her, he left … He was the absolute ruler of his hidden concrete kingdom."

The Austrian authorities say Fritzl imprisoned and repeatedly raped his daughter, Elisabeth, for 24 years in a cramped and windowless dungeon he built beneath the family's home in the western town of Amstetten. Investigators say DNA tests confirm that he fathered her six surviving children. Another child died in infancy.

Fritzl is charged with six crimes, and pleaded guilty to four – rape, false imprisonment, incest and coercion. But he denies murdering one of the seven children, who died shortly after being born and whose body he burned in a stove. He also denies the charge of slavery.

Yesterday, Fritzl was led into the court in handcuffs, but, at first held a ring binder in front of his face and ignored every question asked of him by the media. After the media was sent out, he put down the file and stared straight ahead.

In her opening statement Ms Burkheiser said Fritzl didn't talk to his daughter during her first nine years in captivity and that he simply came down to the cellar to rape her.

"Josef Fritzl used his daughter like his property," Ms Burkheiser said, adding that for her first delivery he gave her an unsterilised blanket to wrap up the infant and a book of childbirth instructions – but only because Elisabeth urged him to.

She alleged that Fritzl once punished the young woman by shutting off electricity to the dungeon, and forced her to spend the first part of her captivity in a tiny space that didn't even have a shower or warm water.

"The worst was … there was no daylight", Ms Burkheiser said, adding it was also "incredibly humid" in the cramped space and the air was mouldy and stale. She said Elisabeth was "broken" by Fritzl's alleged actions and the uncertainty of her fate and that of her children.

At one point Ms Burkheiser, 32, made a mark on the entrance door to the court at 1m 74cm to illustrate the height of the ceiling at the highest point of the dungeon. She added: "They had to crawl on their knees in order to get around the dungeon. It was damp and mouldy."

She then approached the jury with a box of toys and scraps of cloth taken from the cellar and said: "Smell these things."

Members of the jury did so and flinched. She added: "Look at him, with his polite demeanour. He will present to you a caring side, a selfless person, the nice man from next door. What really troubles me is that he has not shown a single sign of regret."

She outlined how Fritzl, a building engineer, was concerned that his teenaged daughter was sliding into a life of debauchery and tricked her into helping him fix a door in the cellar that he had secretly built beneath the family home in 1984. A cloth soaked in ether was placed over her mouth and she was locked in the cellar.

"The second day," said Ms Burkheiser, "he came down and chained her up and raped her. He said nothing to her."

Outlining the most serious of the six charges Fritzl faces – murder – she spoke of how baby Michael, born in 1996, began to turn blue and have trouble with his breathing shortly after birth. "By not offering any assistance as the father, that is murder under Austrian law," she said. "He died two and a half days later. We say that is murder by negligence."

As part of his defence Josef Fritzl claimed he had been abused as a child and that his mother considered him "Satan".

In a trembling voice Mr Fritzl, 73, said: "I had a very difficult childhood. My mother didn't want me … She simply didn't want a child and she treated me correspondingly. I was beaten." At the age of 12, Fritzl began to defend himself. He said: "From that point on, I was Satan personified for her."

Later, Rudolf Mayer, the accused's defence lawyer, insisted that Fritzl was "not a monster". Mr Mayer said: "If you just want to have sex, you don't have children. As a monster, I'd kill all of them downstairs."

Prompted by the judge several times, Fritzl pleaded "partially" guilty to rape. Austrian law differentiates between the severity of rapes and levels of coercion and takes into account the degree of violence used and the consequences for the victim.

The trial is expected to end by Friday, possibly even Thursday. The only witnesses will be Elizabeth and her brother, Harald, both of whose statements have been pre-recorded.

The six surviving children, together with Elisabeth, were initially treated in a psychiatric clinic and then were moved to a secret location. Seeking refuge from reporters, they have since returned to the clinic.

Kerstin, 20, Stefan, 19, and six-year-old Felix remained underground until their release. Lisa, 18, Monika, 16, and Alexander, 13, were taken to live upstairs in the house because Fritzl feared he was running out of space in the dungeon. He told his wife Rosemarie they had been dumped on the doorstep by the "missing" Elisabeth who had joined a cult.

Last night, Fritzl was returned to prison, where guards have described his behaviour as "normal and polite".