Adelaide Archbishop Philip Wilson, the most senior Catholic official in the world to be charged with covering up child sexual abuse, has been found guilty by a NSW court.

Magistrate Robert Stone told Newcastle Local Court on Tuesday Wilson had concealed the abuse of two altar boys in the NSW Hunter region by pedophile priest James Fletcher by failing to report the allegations to police.

Mr Stone said he was satisfied one of the altar boys, Peter Creigh, had been a "truthful and reliable" witness.

In a statement issued by the Catholic Church, Wilson said he was "disappointed" by the decision.

AAP

"I will now have to consider the reasons and consult closely with my lawyers to determine the next steps," he said.

Prosecutor Gareth Harrison had claimed Wilson was involved in a cover-up to protect the church's reputation and there were doubts about his honesty.

Mr Harrison argued that in Wilson's mind victims came second.

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Wilson, 67, who is suffering from the early stages of Alzheimer's disease but claims medication has helped his memory, told the court during his landmark magistrate-only trial he could not remember Mr Creigh and another altar boy telling him in 1976 they were abused by Fletcher.

The prosecution argued Wilson failed to give details to police about a serious indictable offence after Fletcher was arrested in 2004 and went on trial for preying on another young boy.

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Fletcher was found guilty in December 2004 of nine counts of child sexual abuse.

He died in jail of a stroke in January 2006.

But the defence claimed Wilson was not guilty because the case was circumstantial and there was no evidence to prove the archbishop was told about the abuse, believed it was true or remembered being told about it.

Defence barrister Stephen Odgers SC urged the magistrate to take into account that back in the 1970s a priest having sex with a boy was not considered a serious indictable offence.

He said it would have been viewed as an act of indecency, not indecent assault, if the victim could not prove he had been forced to perform sex acts.

Mr Creigh said he had trusted Wilson - then an assistant priest - would take action after he told him Fletcher had repeatedly abused him in 1971 when he was 10.

Mr Creigh claimed Wilson had a "look of horror" on his face when he told him, but the clergyman took no action and didn't it to police.

The defence did not challenge Mr Creigh's truthfulness but raised concerns about the reliability of his memory of what happened in 1976.

Another former altar boy, who can't be named, said he was about 11 in 1976 when he went to confession and told Wilson that Fletcher had abused him.

The witness said Wilson refused to believe him because Fletcher "was a good bloke" and ordered him to get out of the confessional box and say 10 Hail Marys as an act of contrition.