BBC News, St Poelten, Austria
Mr Fritzl faces charges including rape, incest, and murder
The crimes of which he is accused are almost incomprehensible. And so is the ease with which he is alleged to have committed them.
Police say Josef Fritzl imprisoned one of his own daughters in the cellar of their family home for 24 years, and that, in this cramped network of cells, he sexually abused her and fathered seven children with her.
They say he kept three of those children, too, locked underground.
Now, nearly a year after his arrest, Josef Fritzl is standing trial in the town of St Poelten.
This is where he has been under "investigative custody" since his arrest. His journey to court will be brief - the prison is connected to the courthouse.
Mr Fritzl's alleged crimes spanned nearly a quarter of a century. His trial is expected to last no more than a week.
Among the charges he faces are rape, incest, coercion, enslavement and deprivation of liberty. The most serious charge is murder.
Prosecutors say one of the children Mr Fritzl fathered with his daughter in the cellar fell sick shortly after birth and died.
The 73-year-old Austrian stands accused of murder by neglect. If convicted, he could face life imprisonment.
The daughter at the centre of the case will not be in court but a video recording of her testimony will be played to the eight-member jury.
Mr Fritzl's lawyer has already said his client will contest the murder charge and question whether the "enslavement" charge is appropriate.
Media interest in the case is immense. Opposite the courthouse there is a sea of TV satellite trucks and live camera positions.
The local authorities have also put up a special press tent, where journalists will be kept informed of the proceedings.
Some reporters will be allowed to witness the opening of the trial and the verdict. But the rest of the trial will be held behind closed doors.
Sixty kilometres (37 miles) away from the courthouse lies the town of Amstetten. This is where Josef Fritzl led his double life - one family upstairs, and one secret family down below.
The media are out in force
The now empty Fritzl house has become an unwanted tourist attraction, drawing visitors like a magnet. The building is all locked up.
But people take pictures of the "House of Horrors" on their mobile phones. Television crews compete to find new angles of one of the world's most infamous houses.
The people of Amstetten are embarrassed and annoyed.
"It really bothers me when people think Amstetten is a bad place because of Fritzl," one woman tells me.
"I've seen cars with Amstetten number plates being refused petrol at some gas stations outside town - just because of this town's reputation."
"There are black sheep everywhere," one man complains. "Not just in our town. Not just in Austria. But all over the world."