The Austrian incest father Josef Fritzl seemed to have made it easier for everyone by admitting to all the charges against him, including the murder of his son.
The prosecution labels it a case of negligent homicide as he allowed the child Michel Fritzl to die. He is also alleged to have burnt the dead body in a stove in the cellar where he had imprisoned his daughter Elisabeth.
Besides he admitted to a charge of slavery, which he had previously denied.
Fritzl told the jury Wednesday: "I plead guilty to all the charges in the indictment."
He said he had had a change of heart after listening to 11 hours of pre-recorded evidence from Elisabeth, in which she described in harrowing detail her ordeal at his hands.
Asked by judge Andrea Humer what had caused him to change his plea, he replied: "My daughter's videotaped testimony." He added: "I'm sorry."
It means the trial could draw to a close as early as today, as the jury will no longer have to return a verdict and all that remains is for the judges to determine his sentence.
Negligent homicide carries a maximum sentence of life imprisonment, though a life term is not mandatory, and so it is possible that Fritzl changed his plea in a desperate last-minute bid to get a shorter sentence.
Fritzl's sudden about-turn may also have been influenced by a report from a neo-natal specialist, read to the jury on Tuesday afternoon, which said Michael could have survived if he had been taken to hospital when he developed breathing difficulties hours after his birth in 1996.
Instead of seeking medical help, Fritzl is alleged to have told his daughter Elisabeth "what will be, will be," and allowed the child to die three days later.
Fritzl had already admitted charges of rape, incest, false imprisonment and coercion relating to the 24 years in which Elisabeth was imprisoned in the dungeon in Amstetten.
There are some reports that the horribly abused daughter was in the public gallery, incognito, and her sight could have unnerved him.
Josef Fritzl made this decision to change his plea without consulting his lawyer, Rudolf Mayer.
Mr Mayer told BBC that his client had been emotionally "destroyed" by his daughter's testimony - and that he had finally begun to understand something of what she had been through.
It was a huge turnaround, he said, for a man who was not "normal," a man who had an overwhelming urge to dominate and control.
That was also the message of psychiatrist Adelheid Kastner, who met Fritzl several times and put together a psychological profile of him for the court.
Addressing the court from the bench, she said Fritzl's "basic need was for power."
"It is about domination, about power, about control," she said.
She said Fritzl knew he was acting against all the rules, that he knew what he was doing was wrong.
As Dr Kastner described the accused's childhood and his difficult relationship with his mother, who had seen him as "a burden and a calamity", Fritzl stared ahead, twisting his thumbs.
Dr Kastner said that he had picked out his third daughter as his victim because she was the most similar to him, "obstinate and strong."
She said it was more "satisfying" to him to control a strong personality.
He was determined to have someone who belonged to him alone, the psychiatrist said.
She said the large number of children he fathered only strengthened the control he had over his victim.
She recommended that Fritzl be held in a psychiatric facility, as she said there was a danger that he would repeat his behaviour if left untreated.
After the psychiatrist's testimony and brief consideration of reports about the cellar, officials adjourned the trial until Thursday, when the verdict and sentencing are expected.