Australia’s highest court has overturned the conviction of Cardinal George Pell, the most senior Catholic cleric ever to be convicted of child sex abuse.

He was sentenced to six years in prison in March 2019, but Monday’s ruling will free him.

The High Court found that the unanimous jury that convicted him in 2018 “ought to have entertained a doubt as to the applicant’s guilt with respect to each of the offences for which he was convicted,” and it ordered that verdicts of acquittal be entered.

Pell was convicted in December 2018 of abusing two choirboys while he was archbishop of Melbourne in the 1990s.

The decision means he will be released from Barwon Prison outside Melbourne after having served 13 months of the six-year sentence.

The High Court found that the Court of Appeal of the Supreme Court of Victoria, which upheld Pell’s sentence last year, “failed to engage with the question of whether there remained a reasonable possibility that the offending had not taken place.”

Pell was convicted of assaulting the 13-year-old boys after he caught them swigging sacramental wine in a rear room of St. Patrick’s Cathedral in Melbourne in late 1996. The jury also found Pell guilty of indecently assaulting one of the boys in a corridor more than a month later.

He has denied the allegations.

Pell was largely convicted on the testimony of one of the choirboys, now in his 30s with a young family. He first went to police in 2015 after the second alleged victim died of a heroin overdose at age 31. Neither can be identified under state law.

Director of Public Prosecutions Kerri Judd told the High Court last month that the surviving choirboy’s detailed knowledge of the layout of the priests’ sacristy supported his accusation that the boys were molested there.

Pell’s lawyers argued that Pell would have been standing on the cathedral steps chatting with churchgoers after Mass when his crimes were alleged to have occurred, that he was always with other clerics when dressed in his archbishop’s robes, that he could not have performed the sexual acts alleged while wearing the cumbersome garments and that he could not have abused the boys in the busy priests’ sacristy without being detected.

The High Court ruled that unchallenged evidence from a witness was inconsistent with the alleged victim’s account, including Pell’s practice of greeting congregants on the cathedral steps after Mass and the “continuous traffic in and out of the priests’ sacristy” for 10 to 15 minutes after the conclusion of the procession that ended Mass.

Download the NBC News app for breaking news and politics

The High Court found that even if it found the alleged victim’s account to be credible, the evidence from the other witness “nonetheless required the jury, acting rationally, to have entertained a reasonable doubt as to the applicant’s guilt in relation to the offences involved in both alleged incidents.”

The Victoria state Court of Appeal rejected Pell’s appeal in August by a 2-1 majority ruling. The High Court decided in November to hear Pell’s appeal, which was his last chance to overturn his convictions.

Victoria Police said in a statement that it respected the decision of the High Court, according to NBC News partner 7News in Australia.

“Victoria Police remains committed to investigating sexual assault offences and providing justice for victims no matter how many years have passed,” police said in the statement, adding that it acknowledged the “tireless work on this case” by task force investigators.