Josef Fritzl's psychological abnormalities should be regarded as extenuating circumstances in any sentence handed down at his trial in Austria, his lawyer said on Thursday.
"Extenuating circumstances must be taken into consideration," Rudolf Mayer told jurors in his closing statement on the final day of the trial.
"Regarding the charge of murder, I don't believe it was," Mayer said. "My client was responsible for his actions, but his personality has psychological abnormalities. He didn't choose to be the way he is."
Fritzl faces life imprisonment for murder by neglect, over the death of one of seven babies he fathered with his daughter Elisabeth during 24 years of sexual abuse.
On Wednesday, the pensioner dramatically changed his plea to guilty on charges of murder and enslavement, although he had earlier rejected those two charges.
He had already pleaded guilty to incest, rape, sequestration and grievous assault, for holding Elisabeth, 42, and three of their children captive in a damp dungeon.
Mayer also rejected chief prosecutor Christiane Burkheiser's assertion that Fritzl was "trying to exploit people's gullibility" and dupe the jury with his sudden about-turn.
"It cannot be said that he was pretending," Mayer said.
Fritzl said he had a change of heart after seeing his daughter's video testimony about her ordeal for the first time.
"He broke down. It was a shock," said Mayer of his reaction to the testimony and Elisabeth's sudden appearance in the courtroom on Tuesday while Fritzl was being questioned.
"At the last minute, my client realised that Elisabeth was sitting there."
The verdict in the four-day trial was expected Thursday afternoon.
Psychiatrist Adelheid Kastner, who spent dozens of hours speaking with Fritzl, concluded in a report that he was responsible for his actions over the past quarter of a century but suffered personality problems.
She however told the court Wednesday that Fritzl, who felt he was "born to rape," risked re-offending and should be sent to a facility for mentally abnormal offenders.