Pope Benedict XVI's former butler is to go on trial next week in the Vatican City charged with aggravated theft.
Paolo Gabriele has already admitted taking confidential documents and leaking them to the Italian media.
The 46-year-old is expected to argue that he was inspired by the Holy Spirit to take the papers in order to expose "evil and corruption" in the Church.
He faces up to six years in prison if found guilty. A second Vatican worker will be tried on a lesser charge.
Mr Gabriele is currently under house arrest at his Vatican City home after being held in solitary confinement for nine weeks. His lawyer resigned last month in an apparent disagreement over defence strategy.
He will stand trial on 29 September alongside computer technician Claudio Sciarpelletti, who is accused of aiding and abetting a crime.
A pool of just three journalists will be allowed inside the Vatican City courtroom. No TV cameras will be permitted.
Mr Gabriele has admitted he was the source of the leaked letters taken from Vatican offices and published in the controversial book, His Holiness, by an Italian investigative journalist in May.
The so-called "Vatileaks" scandal has exposed alleged corruption and internal conflicts at the Holy See.
Pope Benedict has set up a special commission of cardinals to look into the circumstances of the theft, but their findings have not been made public.
Some 30 clerics and lay employees who work inside the central administration of the Roman Catholic Church have been questioned by the Cardinals and by Vatican police, says the BBC's David Willey in Rome, but so far no ecclesiastic has been charged in connection with the theft.
The Vatican is anxious to conclude the fallout from this embarrassing scandal before bishops from around the world begin arriving next month for an important Vatican conference on how to continue spreading the bible message in an increasingly secularised world, our correspondent says.