John William Chute, 83, and Gregory Joseph Sutton, 64, were among four men police charged with fresh offences as part of an ongoing investigation into child sexual abuse in ACT schools in the 1980s.

Chute did not appear in court to face two charges of indecent assault on a male and two acts of indecency on a person aged between 10 and 16.

His defence lawyer told Magistrate Bernadette Boss his client was infirm and suffered from Parkinson's disease and dementia.

The court heard Chute, known as Brother Kostka, was the subject of separate charges in NSW that were set to come before court on Friday.

He had been assessed by experts to determine whether he could be declared unfit for trial.

Sutton has been charged with three indecent assaults on a male and was in court when his case was briefly mentioned.

His defence lawyer indicated an application for a permanent stay on proceedings would likely be lodged on Sutton's behalf. No further details of the circumstances surrounding the pair's alleged offending were revealed.

Both cases will be back in court on March 8.

Past abuse by Sutton and Chute at schools associated with the Catholic Marist Brothers organisation, including Marist College Canberra, was closely examined during the Canberra hearings of the child sexual abuse royal commission.

The royal commission found that the organisation moved Sutton and Chute to different schools when it received complaints that they were inappropriately touching children.

The commission found Marist Brothers' actions enabled Sutton and Chute to continue to access children throughout the 1980s and early 1990s.

A third man, David Kisun, 69, was also set to face court on Tuesday but did not appear. He has also been summonsed to appear on three indecent assault offences. The ACT Magistrates Court heard there was no formal proof that Kisun had been served with the summons.

A fourth man from NSW, aged 60, is set to face court on Thursday.

ACT Policing set up Operation Attest in February last year in response the royal commission.

New laws introduced into the ACT Legislative Assembly in 2013 cleared the path for certain historical sexual offences, committed between 1951 and 1985, to be prosecuted.

Acting Detective Superintendent Marcus Boorman on Tuesday praised the bravery of those men who had come forward under Operation Attest, and acknowledged the trauma they had endured for much of their lives.

"I can only imagine how difficult is for these people," he said.

"We can only imagine the damage and the difficulties that they've had to deal with as they've grown up in life."

Acting Superintendent Boorman encouraged more victims to come forward, saying the operation was ongoing, and would look at all complaints that were made.

"The courage that has been shown by these previous men who have come forward [shows] to these other people that they will be heard, [their complaints] will be investigated, and if the evidence is there, a prosecution will take place," he said.

"I'm sure there's more victims out there, but again, I keep saying that these crimes committed against these people are heinous … and you can only imagine the kind of damage that it's caused."