“Light off: rape.” To make the point, the Austrian prosecutor Christiane Burkheiser threw the switch in the courtroom. “Light on. Josef Fritzl leaves the cellar.”

The trial of Fritzl – on charges of imprisoning and raping his daughter for almost a quarter of a century and murdering one of the seven children he fathered with her – was never going to be routine. It was indeed billed as Austria’s Trial of the Century.

But no one had reckoned with the concentrated drama that was packed into the first day of hearings – from the moment Fritzl appeared with his head buried in a blue folder to shield him from the cameras, to the prosecution’s attempts to recreate the atmosphere of the dungeon, to the claims by his defence that he was no monster but a caring family man.

Ms Burkheiser’s task was to make the jurors feel like temporary prisoners of Fritzl. First, she had the height of the adapted cellar – he had told the authorities he was building a nuclear bunker – marked on the doorpost of the courtroom in St Pölten: 1.78 metres (6ft). Then, she passed to the jury objects retrieved from the cellar where Elisabeth gave birth to her children. “Smell!” said the prosecutor. And the jurors retched at the sheer pungency of 24-year-old mould.

“They had to crawl on their knees in order to get around the dungeon,” she told the court. “It was damp and mouldy. The dampness crept into their backs and into their bones.”

To drive home her point, the prosecutor threaded the phrase “light on, light off” throughout her speech. Fritzl, she made clear, wanted absolute control over his downstairs family.

Was Ms Burkheiser’s performance enough to transport the eight jurors underground? Or to discomfit Fritzl? The 73-year-old building engineer had entered the courtroom hiding his face behind the folder, his hands quivering, besieged by questions from the waiting media.

“How do you explain yourself? How can you abuse your daughter for 24 years?” asked Austrian television reporters, thrusting their microphones into the dock. He did not answer. Fritzl did eventually speak, after the cameras were excluded from the courtroom. Only then was the face exposed.

The voice, confirming his identity and marital status, was reedy, had none of the deep timbre that had been associated with the man who fathered 13 children, seven of them in an incestuous relationship with his imprisoned daughter. And the face – so tanned when he abandoned his entombed family for a month to take a holiday in Thailand – was parchment yellow, a prison complexion.

He had pleaded guilty or, as he said, partially guilty to rape – the prosecutor calculated that he raped his daughter 3,000 times – to coercion, to forced imprisonment, to incest. Not guilty to murdering one of his daughter’s babies – neglected so badly that he died, blue in the face, two days after birth – and not guilty to enslavement.

The pleas had been widely expected as had the essence of his defence, that he was no monster but rather a frustrated, violent father who cared for his so-called second family. “The exceptional aspect of this case is that my client did not behave like a monster,” said Rupert Mayer, his defence lawyer. “The special point is that he chose his daughter for this role, that he created children together with her and looked after them . . . he bought them schoolbooks, celebrated Christmas and birthdays with them.” He appealed to the jury to be objective. “If you just want to have sex, you don’t have children,” Mr Mayer said. “As a monster, I’d kill all of them downstairs.”

For his part, Fritzl told the three judges and eight jurors that he, too, had suffered abuse as a child. “I had a very difficult childhood,” he said in a trembling voice. “My mother didn’t want me. She was 42 when she had me – she simply didn’t want a child and she treated me correspondingly. I was beaten.” At the age of 12, he said, he had made it clear to his mother that he would not tolerate being beaten any longer and would defend himself. “From that point on, I was Satan personified for her,” he said. She never showed him any affection and his father appeared only “rarely and sporadically”.

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