Paolo Gabriele, 46, claims he leaked the papers in a bid to expose corruption in the Vatican.
Gabriele served Pope Benedict XVI’s meals and helped him dress in his capacity as butler.
He is now being tried along with a Vatican computer expert in the city state’s little-used tribunal, a small wood-panelled room with a papal emblem on its ceiling.
At the short hearing, the judges dismissed some evidence gathered during the investigation into Gabriele and decided to separate the trials of Gabriele and his co-defendant.
Gabriele faces up to four years in prison if convicted of aggravated theft. He has already confessed, saying he leaked the documents to shed light on what he called the “evil and corruption” in the Roman Catholic Church, and has asked to be pardoned by the pope.
Judge Giuseppe Dalla Torre set the next hearing for Tuesday, when Gabriele will be questioned.
Gabriele was arrested in May after police found confidential documents in his apartment inside the Vatican, throwing a global media spotlight on an institution battling to defend its reputation.
A three-judge panel will decide the fate of Gabriele, whom the pope used to call “Paoletto”, now described in Vatican documents as “the defendant”.
The self-styled whistle-blower, who says he was trying to expose graft at the headquarters of the Roman Catholic Church, is charged with aggravated theft for stealing and leaking the pontiff’s personal papers.
Only eight journalists were allowed into the courtroom yesterday, who were to brief other reporters after the end of the first session.