Australia's most senior Catholic Archbishop accused of covering up child sexual abuse has had his trial delayed because of medical issues.

Philip Wilson, the Archbishop of Adelaide, was due to front Newcastle Local Court today, but had a pacemaker fitted six days ago and remains in South Australia.

He was arrested two and a half years ago, and has tried, and failed, three times to permanently stay proceedings.

However, Archbishop Wilson's barrister Stephen Odgers today said his client was keen to have his day in court.

"I'm confident that the advice I've received is that one week is OK and he will be able to fly up here on Wednesday afternoon," Mr Odgers told the court.

"The defendant is very keen to participate in the trial."

The abuse was alleged to have been carried out by paedophile priest Father Jim Fletcher in the Maitland-Newcastle Catholic Diocese.

Archbishop Wilson is accused of doing nothing after being told about abuse by Fletcher in the 1970s.

Mr Odgers also raised questions about Archbishop Wilson's cognitive state, telling the court his client had reduced functioning in his left temporal lobe.

Because of that the barrister said: "There are serious problems with respect to the defendant participating in the trial … with the possibility of him giving evidence."

Magistrate Caleb Franklin is considering an application to delay the trial due to Archbishop Wilson's cognitive state.

Archbishop Wilson's lawyers today told the court he had Alzheimer's disease, and needed medication that could take months to work.

Archbishop Wilson's trial is seen as a landmark test case, after scores of cover-up allegations were made at hearings held by the Royal Commission into Institutional Responses to Child Sexual Abuse.

Three failed appeals

Archbishop Wilson is the most senior Australian Catholic clergyman to be charged with the offence.

At the time of Fletcher's alleged abuse, Archbishop Wilson was an assistant parish priest in East Maitland and worked with the paedophile priest, who died in prison in 2006.

Police alleged that between 2004 and 2006, Archbishop Wilson had information which might have helped police secure Fletcher's conviction.

Archbishop Wilson has retained his position amid the criminal proceedings.

Earlier this year, he lost an attempt to rule the charges invalid in Sydney's Court of Appeal.

Two separate applications were previously rejected by a magistrate and a Supreme Court judge.

In court today, crown prosecutor Gareth Harrison, questioned the timing of the surgery to install the pacemaker.

"The accused was charged more than two and a half years ago, he hasn't been required to appear in court until today, and five days before ... he seems to have had a pacemaker installed," he said.

"The prosecution are pretty much in the dark in relation to the cardiovascular problems ... [the doctor] hasn't returned our calls."

Today, prosecutors showed the court a YouTube video sermon by Archbishop Wilson three weeks after an alleged fall in October.

The prosecution said he appeared lucid, but neurologist Andrew Lee said "his fluency is not completely normal, he stumbles across a number of words".

The matter has been adjourned until Friday to set a new hearing date.