Pope Benedict's former butler is to give evidence for the first time on Tuesday on the second day of his trial for stealing documents he hoped would expose corrupt dealings in the Vatican.
Paolo Gabriele, 46, an unassuming and devout servant who prompted a crisis in Benedict's papacy after he slipped sensitive documents to an Italian journalist, has not spoken publicly since he was arrested in May.
The testimony of the manservant - a member of the Vatican's most inner circle, the "papal family" - will be closely followed for hints on what prompted him to betray the man Catholics consider Christ's vicar on earth.
The papers Gabriele admits he photocopied and passed on at secret meetings included letters to the pope in which a senior Vatican functionary expressed concern about improper behavior in the Holy See's business dealings.
The leaks were a blow to the Vatican, which has been eager to clean up its image after a series of scandals involving its bank. The letter-writer, Archbishop Carlo Maria Vigano, was later posted to Washington despite pleading to be allowed to remain at the papal state.
The case, dubbed "Vatileaks", saw the butler imprisoned in the Vatican police station while investigators seized 82 boxes of evidence from the apartment where he lived with his wife and three children.
Conducted under a 19th-century criminal code, the trial began with a setback for the defense on Saturday when judges refused to admit evidence from the Church's own investigation.
Gabriele's lawyer, Cristiana Arru, hoped to explain her client's motives by admitting as evidence an inquiry by a commission of cardinals who questioned Vatican employees about the leaks.
A summary of the inquiry's results released in August showed Gabriele acted because he saw "evil and corruption everywhere in the Church," and felt the pope was not sufficiently informed.
But chief judge Giuseppe Dalla Torre said the commission of cardinals answered only to the pope and that the inquiry had "no relevance" to Vatican City's penal code.
Only evidence gathered by a prosecutor and the Vatican police will be allowed.
Facing charges of aggravated theft, the man who helped the pope dress and rode in the front seat of the Popemobile could now face up to four years in an Italian prison.
Another man, Vatican computer expert Claudio Sciarpelletti is on trial separately for aiding Gabriele.