Josef Fritzl, the Austrian accused of imprisoning his daughter and fathering her seven children, is expected to be sentenced on Thursday after announcing a change of heart and pleading guilty to all charges, including negligent homicide and enslavement.

Josef Fritzl on Wednesday changed his mind and entered guilty pleas to all of the charges he faces. (Helmut Fohringer/Pool/Associated Press)

Fritzl, 73, had pleaded guilty to incest charges this week but denied responsibility for the death of his infant son and the 24 years his daughter spent in a cellar under his home.

But on Wednesday, he told the court at his jury trial in St. Poelten, west of Vienna, that he had decided to acknowledge his guilt.

"I declare myself guilty to the charges in the indictment," he told Judge Andrea Humer and the eight-person jury, referring at one point to what he called his "sick behaviour."

When asked by the judge what changed his mind, he indicated it was the videotaped testimony of his daughter Elisabeth that the court had viewed during a closed-door session Tuesday.

Fritzl's lawyer, Rudolf Mayer, said the testimony "must really have shaken him up."

However, a person familiar with the trial told the Associated Press that Elisabeth herself was in the courtroom on both days when the public and media were excluded — suggesting her presence alone might have unnerved Fritzl and prompted him to change his pleas.

The person spoke on condition of anonymity because he was not authorized to discuss the closed-door proceedings, AP said. Before the trial, prosecutors had said Elisabeth would not be present and would testify only through prerecorded remarks.

Court spokesman Franz Cutka said Elisabeth was not in court Wednesday. He seemed to confirm she was in court earlier this week by saying neither he nor the president of the court personally greeted her.

With proper care, boy might have lived: prosecutors

A formal verdict and sentencing are expected Thursday after closing statements from both sides, AP said. Fritzl faces a maximum sentence of life imprisonment on charges of rape, incest, coercion, false imprisonment, enslavement and negligent homicide.

Prosecutors said that if he had arranged proper medical care for the infant boy, who was born in April 1996, he might have survived.

Fritzl expressed regret over the infant's death Wednesday.

"I don't know why I didn't help," Fritzl said. "I just overlooked it. I thought the little one would survive. I should have recognized that the baby was doing poorly."

Wearing a mismatched suit and a blue shirt, Fritzl did not hide his face behind a binder as he had done for the last two days when led into the courtroom.

Fritzl still poses threat: psychiatrist

Psychiatrist Adelheid Kastner testified Wednesday she believes Fritzl has a serious personality disorder and would pose a threat if freed. Fritzl has a need to control people and should serve out his sentence at a psychiatric facility, she testified.

She said Fritzl had an ability to block out his crimes but knew what he was doing was wrong, acknowledging he had a guilty conscience when he went to bed at night and when he woke up in the morning.

Elisabeth, who is now 42, and her six surviving children are being treated in a psychiatric facility at an undisclosed location. Three of the children, who range in age from six to 20, didn't see daylight until Fritzl was arrested 11 months ago.

The trial is closed to the public and court officials are only providing brief explanations of what happened inside the courtroom to journalists at the end of each day.

With files from the Associated Press