The pope's once-trusted butler went on trial Saturday for stealing papal documents and passing them off to a journalist, in a case that embarrassed the Vatican but may shed some light on the discreet, internal workings of the papal household.

Former butler Paolo Gabriele is accused of photocopying the pope's correspondence and giving it to Italian journalist Gianluigi Nuzzi, whose book "His Holiness: The secret papers of Pope Benedict XVI," was published to great fanfare in May.

Prosecutors claim Gabriele confessed to having taken the documents in order to expose the "evil and corruption" in the church.

On Saturday, the court said the pope's personal secretary, Monsignor Georg Gaenswein, had been called as a witness. His testimony is sure to attract attention given that Gaenswein rarely speaks in public, much less about the details of the tightly-knit papal family of which Gabriele was a part.

Other witnesses include one of the four consecrated women who take care of the pope's apartment, a monsignore in the Vatican secretary of state, a Swiss Guard commander and the head of the Vatican police force.

Judge Giuseppe Dalla Torre set the next hearing for Tuesday, when Gabriele will be questioned. He said he thought the whole trial could be wrapped up in four more hearings.

Gabriele faces up to four years in prison if he is convicted. He has already asked to be pardoned by the pope, something most Vatican watchers say is a given.

Gabriele, a 46-year-old father of three, appeared calm but tense during the two-hour hearing, frequently crossing his hands or clasping them in his lap while sitting alone on a bench on one side of the intimate, austere courtroom, following the proceedings impassively. During a break in the hearing, he chatted with his attorney, Cristiana Arru, and greeted journalists with a nod and a smile as he entered and exited.

Arru raised a series of objections at the start of the hearing, only some of which were accepted by the court. One concerned two jailhouse conversations Gabriele had with the head of the Vatican police force without his lawyers present. The judges declared both inadmissible. The content is not public.

Arru also sought access to the report of a commission of cardinals appointed by the pope to investigate the leaks alongside Vatican magistrates. The court denied the request.

The attorney for co-defendant Claudio Sciarpelletti successfully petitioned to have his client's trial separated from that of Gabriele. Sciarpelletti wasn't in the courtroom on Saturday.

Neither Gabriele's wife nor any of his three children attended the hearing. Space for the public was limited; eight of the 18 seats were taken up by the journalists who followed the proceedings and then briefed the rest of the Vatican press corps afterward.

Security was relaxed, with the guards at the tribunal entrance mostly concerned that none of the press or public brought in any recording devices: They even checked pens to make sure they couldn't record, and sequestered cell phones in safety deposit boxes. No television or still cameras were allowed, except for Vatican media, which filmed the first moments of the hearing.

Given the content of the leaks and the Vatican's penchant for secrecy, the fact that the trial was open to the public and media might seem unusual. In fact, such trials in the Vatican's civil and penal tribunal are routinely public. They just don't happen very often or attract much attention. The Vatican's ecclesiastical courts, on the other hand, which handle marriage annulments, clerical sex abuse cases, and other matters of church law, remain firmly off-limits to outsiders.

In some ways, the willingness of the Vatican to proceed with the trial at all is an indication of its efforts to show transparency in its inner workings. Benedict could have pardoned Gabriele as soon as he was arrested or charged, precluding any trial from getting off the ground. Instead he allowed the trial to proceed.