Wilson, the most senior Catholic official in the world to be charged with concealing child sexual abuse, was cross-examined by prosecutor Gareth Harrison on Thursday in Newcastle Local Court.

When asked what would it take for him to believe abuse allegations by four boys the archbishop said he would only believe it if a priest confessed or was found guilty at trial.

''In forming a belief, in every case, belief has to be based on an admission or the end of a trial with a conviction," the 67-year-old told the court.

Wilson said he believed just two of the four boys who claimed to have been abused by pedophile priest James Fletcher - altar boy Peter Creigh and another boy, who can't be named for legal reasons, who gave evidence at Fletcher's 2004 trial.

Fletcher was found guilty in December 2004 of nine counts of child sexual abuse and died in jail of a stroke in 2006.

Wilson on Thursday said he only believed Mr Creigh after hearing him give evidence in December 2017 detailing how Fletcher preyed on him in 1971 when he was 10.

Mr Creigh claims he told Wilson - then an assistant priest - about the abuse in 1976 because he thought he could trust him and he'd report Fletcher.

Mr Creigh says he told Wilson, who did not go to the police, that Fletcher claimed the abuse was punishment for not doing his job properly as an altar boy.

Wilson, diagnosed with the early stages of Alzheimer's disease, claims to have no memory of the alleged 1976 conversation with Mr Creigh.

The archbishop believes the conversation likely never happened because he would have remembered to this day if a teenage boy had told him in graphic details how a fellow priest abused him.

Wilson also told the court on Thursday about an "awkward" conversation he had with Fletcher in the Hunter region just weeks before the priest was due to stand trial.

Wilson met Fletcher in late 2004 a day after a family told him their son - not the boy who'd give evidence against Fletcher at trial - had been abused by the priest.

Wilson, who'd worked in the same parish as Fletcher and lived with him briefly in the 1980s, said he visited the priest's mother to offer her support.

The archbishop had been there for about 20 minutes when Fletcher appeared unexpectedly. They then talked for a few minutes.

Wilson did not ask Fletcher about the alleged abuse.

"It's not the sort of thing you go around inquiring about ... it was an awkward situation," Wilson said.

"I didn't go there to discuss the allegations of his behaviour."

Asked by Mr Harrison if he had wished Fletcher well for his upcoming trial, Wilson said: "No, I didn't."

Wilson denied the meeting with Fletcher would have triggered his memory of the alleged conversation he had with Mr Creigh in 1976.

Wilson, who has never reported child sexual abuse by another priest to the police, says he has no memory of seeing a second altar boy in 1976 who claimed Fletcher abused him.

The trial is expected to end on Friday with magistrate Robert Stone reserving his decision. Wilson faces a maximum two years in jail if convicted.

Australian Associated Press