(RNS) The Vatican on Tuesday (Oct. 2) launched an investigation after Pope Benedict’s former butler alleged he was mistreated during the first weeks of his two-month detention in a Vatican jail.

Paolo Gabriele, or “Paoletto” as he was known in the papal apartments, was interrogated on the second day of his trial at the Vatican on charges of stealing the pontiff’s private papers and leaking them to the press.

He told judges how he spent “15 to 20 days” in a cell so small that he couldn’t “even stretch his arms.” The light was kept on 24 hours a day, “slightly damaging" his eyesight, he added, and he felt under “psychological pressure.”

A Vatican judge immediately opened an investigation into the butler's allegations. The Vatican Gendarmeria, or police, responded in a statement that the light was left on to guarantee Gabriele's own security, and that the cell “was in line with other countries' standards for similar situations.”

During Tuesday’s hearing, Gabriele pleaded not guilty to the charge of “aggravated theft” leveled against him. But he added that he felt “guilty of betraying the pope’s trust."

The so-called Vatileaks scandal exposed allegations of corruption, infighting and personal rivalries inside the secretive top echelons of the Catholic Church, and proved a major embarrassment for the Vatican.

According to a pool of reporters in the small Vatican courtroom, Gabriele looked at ease as he responded to questions posed by the tribunal’s president, Giuseppe Dalla Torre, by prosecutor Nicola Picardi and by his lawyer Cristiana Arru.

Benedict’s former personal assistant, tasked among other things with serving the pope's meals and arranging his clothes, recalled how he came to believe that the pope could be easily “manipulated.”

As he was invited to sit down with the pontiff and his staff at meals, Gabriele said he could gauge “how differently some things were perceived by the people and by those in power.” He also noticed that the pope “asked questions about things he should have been informed about.”

“I became convinced that it was easy to manipulate someone with such a huge power,” he explained.

While he had told Vatican investigators previously that he felt like an “infiltrator” of the Holy Spirit and that he wanted to give a “media shock” to a church he saw as tarnished by “evil and corruption,” Gabriele admitted to the three-judge panel that he couldn't really explain the motives for his actions.

He described how he had been the recipient of complaints and confessions of dozens of Vatican employees, who turned to him both because of his position and because he never refused to lend them a sympathetic ear.

But the former butler stressed that he had no accomplices, and that the two cardinals and other Vatican officials whom he had named during the investigation were only people with whom he shared the same concerns, not members of a network of conspirators.

Responding to questions by prosecutor Picardi, Gabriele described how he photocopied documents “during office hours” as he helped Benedict’s two personal secretaries in a small office adjoining the pontiff’s private library.

“I made two copies for each document to be able to demonstrate what I was copying. I wasn’t so deluded as to think that I wouldn’t have to pay the consequences,” he told the judges.

He also flatly denied receiving “money or other benefits” for giving the confidential documents to Gianluigi Nuzzi, an Italian investigative reporter who published them in the best-selling book “Sua Santita,” “His Holiness.”

On Tuesday, Vatican judges also questioned five other witnesses, including Benedict’s personal secretary, the Rev. Georg Gaenswein.

Each of them laid one hand on a copy of the Bible and vowed to tell “the whole truth and nothing but the truth.” In the Vatican legal system, Gabriele as a defendant was not required to do so.

Gaenswein looked tense during the hearing and spoke in terse sentences, according to witnesses, ignoring Gabriele as he stood up in a sign of deference.

The pope's secretary said he hadn't suspected Gabriele before evidence began to mount against him on the eve of his arrest. But contradicting Gabriele's statements, he said he could recognize original documents among the thousands of pages found in the butler's apartment.

Among those questioned were Cristina Cernetti, one of the four consecrated women who serve in the papal apartment, and three Vatican “gendarmi,” or policemen. The policemen admitted to not using gloves during the search of Gabriele's apartment, and gave slightly contradictory statements on where a nugget, presumably made of gold, had been found within his house.

The trial resumes on Wednesday with the questioning of more witnesses. According to the tribunal's president, a sentence could be expected by the end of this week.

If convicted, Gabriele faces four year in jail, even though Vatican watchers expect that the he might receive a papal pardon.