MELBOURNE, Australia -- The most senior Catholic to be found guilty of child sex abuse will spend his 78th birthday in an Australian prison on Saturday as three judges consider whether to overturn his convictions on charges of molesting two choirboys in a Melbourne cathedral two decades ago.

The Victoria state Court of Appeal judges on Thursday ended an extraordinarily long two-day hearing of Cardinal George Pell's appeal of his convictions on allegations he orally raped a 13-year-old choirboy and indecently dealt with the boy and the boy's 13-year-old friend in a rear room of St. Patrick's Cathedral in December 1996. Pell had become archbishop of Melbourne, Australia's second-largest city, only months before.

The judges gave no indication of when they would announce their decision, but have said they still need to view more video of witness testimony for clues to how the Victoria County Court jury came to its unanimous verdicts in December. Such appeals usually take less than a day to be heard in court because they are based on less complex issues.

The Pell decision could be weeks away.

Pell sat silently in the dock on both days of the hearing wearing a cleric's collar and occasionally taking notes. He was taken between a Melbourne prison where he has been in custody since March and the court in handcuffs as the lone passenger in a large prison van.

In court on Wednesday, Pell's lawyers described as "impossible" allegations that he molested the boys in a priests' sacristy undetected moments after Sunday Masses while he was dressed in an archbishop's robes.

Prosecutors argued on Thursday that the convictions should not be overturned and described Pell's accuser as believable.

"The complainant was a very compelling witness," prosecutor Chris Boyce said. "He was clearly not a liar. He was not a fantasist. He was a witness of truth."

One of the people Pell is convicted of molesting died of a heroin overdose in 2014 aged 31, apparently without ever alleging he had been abused. State law prohibits identifying either victim.

The other, now in his 30s, became the key prosecution witness. He first came to police in 2015.

Pell was sentenced in March to six years in prison and is being held in special protective custody because pedophiles are regarded as being at higher risk of harm from other prisoners. While he remains Australia's highest-ranking Catholic, the Vatican is conducting its own investigation into his convictions.

Pope Francis' papacy has been thrown into turmoil by clerical sexual abuse and the church's handling of such cases worldwide. In a little more than a year, the pope has acknowledged he made "grave errors" in Chile's worst case of coverup, Pell was convicted of abuse, a French cardinal was convicted of failing to report a pedophile, and a third cardinal, former U.S. church leader Theodore McCarrick, was defrocked after a Vatican investigation determined he molested children and adults.

In addition to the rape and three indecency convictions from the sacristy, Pell was also convicted of an act of indecency against the complainant by squeezing his genitals as they passed in a cathedral corridor immediately after a Mass in early 1997.

Boyce said the complainant spent more than eight hours in the witness box and underwent "searing" cross examination during Pell's original trial in the Victoria County Court, which ended with a deadlocked jury in September last year.

A second jury convicted Pell after watching a video of the complainant's testimony. The appeal judges will also watch the same testimony.

Boyce told the judges they had to watch the complainant's evidence from start to finish.

After hearing the man's responses, "one puts down one's pen and stares blankly at the screen and is moved," Boyce said, adding that at that point any doubts are removed.

Boyce told the judges they need not consider why at least two jurors in Pell's original trial were not convinced beyond reasonable doubt of his guilt.

Whichever way the court rules, the case could reach the High Court, Australia's ultimate arbiter.

If the judges rule that the verdict is unsafe on the evidence, Pell would be acquitted. If they rule there was an irregularity in his arraignment, another of the grounds cited in his appeal, he could be retried. If that happens, he would likely be freed on bail until his third trial.