SANKT POELTEN, Austria, (AFP) - Josef Fritzl changed his plea Wednesday to guilty of murder and slavery in a move that stunned the court hearing how he locked up his daughter for 24 years and forced her to bear seven children. The 73-year-old Austrian said his change of heart had come after seeing his daughter Elisabeth describe her quarter century of sexual abuse in a dark, damp cellar during video testimony played at the trial. "I plead guilty to the crimes I've been charged with," Fritzl told the court. "I'm sorry," he added in a low tone, shocked and shame-faced, almost in tears. The retired electrical engineer had pleaded guilty to incest, rape and sequestration on Monday but denied murder, for which he faces a life prison term, and enslavement, a charge used for the first time in Austria. Asked by the judge what caused him to change his plea, Fritzl replied: "My daughter's videotaped testimony." Fritzl had to watch the testimony on Monday and Tuesday and was questioned about his treatment of her. The Kurier newspaper reported that Elisabeth, now 42, made an unexpected appearance in court while Fritzl was being questioned. Fritzl's lawyer, Rudolf Mayer, would not confirm or deny that she was in court, but fuelled speculation that she had an impact on his decision to change his pleas. "If some of the victims were present (in court) yesterday (Tuesday), that certainly must have had a strong trigger effect," he said. Elisabeth Fritzl and her children have sought refuge in a specialist clinic during the trial to avoid publicity. Authorities are attempting to give them a new start in life under a new identity. The prosecution has accused Fritzl of murder for letting a baby die shortly after birth in the cellar. Fritzl had maintained the baby was stillborn and burnt the body in a boiler. But he admitted Wednesday that he was present at the birth and that it had developed breathing problems. "I don't know why I didn't help," he told the court. "I should have noticed that the baby was not doing well. I just hoped it would survive." A psychiatrist told the court that Fritzl felt he was "born to rape", and said he should be placed in a psychiatric facility because there was a risk he would commit new offences. "The danger is still very much there that he will reoffend if he is not treated," said Adelheid Kastner. "He is aware - he says so himself - that he has an evil side." Out of his seven legitimate children, Fritzl told Kastner he had chosen Elisabeth as his victim, "because she was most like me. She was as stubborn as me, as strong as me." He had told her: "The stronger your opponent, the bigger the victory," she added. During the trial, the jurors have heard how Fritzl used his daughter "as a toy" during her captivity in a narrow cellar with no hot water, no heating, no fresh air or sunlight. Two technical experts also gave a description of the cellar in which Fritzl locked his daughter and the children. Fritzl had initially claimed that a timed mechanism ensured that three electronically-locked doors would open automatically to let the prisoners out, if something happened to him. But the experts found no such installation upon examination of the doors. Three children were brought up to live with Fritzl and his wife Rosemarie while three lived with Elisabeth and never left the dungeon until their release last April. The trial was adjourned so the three judges could prepare questions to help the jury make its verdict. Closing statements were to be given Thursday when a verdict and sentencing is expected.