The most senior Catholic to be convicted of child sex abuse took his appeal to Australia’s highest court Wednesday in potentially his last bid to clear his name.

Cardinal George Pell was sentenced a year ago to six years in prison for molesting two 13-year-old choirboys in Melbourne’s St. Patrick’s Cathedral while he was the city’s archbishop in the late 1990s.

He was convicted by the unanimous verdict of a Victoria state County Court jury in December 2018 after a jury in an earlier trial was deadlocked.

A Victoria Court of Appeal rejected his appeal against his convictions in a 2-1 majority decision in August last year.

Pope Francis’ 78-year-old former finance minister is arguing before the High Court that the guilty verdicts were unreasonable and could not be supported by the whole of the evidence from more than 20 prosecution witnesses who include priests, altar servers and former choirboys.

Seven judges are hearing the case over two days.

Pell’s lawyer Bret Walker told the judges that there had been a “reversal of onus” in which Pell was expected to prove the offending didn’t happen instead of prosecutors proving the crimes were committed beyond reasonable doubt.

“That is a wrong question which sends the inquiry onto a terribly damaging wrong route,” Walker said.

Walker said the allegations that Pell had molested the two boys in a priests’ sacristy moments after a Mass could not be proved if the jury had accepted the evidence of sacristan Maxwell Potter and Monsignor Charles Portelli.

Potter had testified that the sacristy was kept locked during Masses and Portelli had given evidence that he was always with Pell while he was dressed in his archbishop’s robes.