County Court judge Christopher O'Neill on Thursday ruled that Cooper pay his victim $65,000 for pain and suffering caused, and a further $8992 to cover past and future medical expenses and treatment.

Cooper, 57, in 2013 pleaded guilty to indecently assaulting two teenage brothers between 1984 and 1986.

Cooper, whose now-disgraced career included stints as a Crown prosecutor and a magistrate, had a three-year jail term wholly suspended.

Judge O'Neill found Cooper's offending had triggered his victim's physiological problems, including post traumatic stress disorder, a major depressive disorder and struggles with panic attacks, anxiety, shame, guilt, embarrassment and anger.

Outside court, the man, who cannot be named, said there was no monetary sum that could be put on the suffering he, his brother and parents had endured, but welcomed the chance to seek compensation as a victim of crime.

"This will send another sign to the community that everyone should have confidence in the system - the judges, the courts, the police - to step forward and just tell the truth," he said.

"For me, unfortunately I kept this in for 35 years and I paid that price in terms of 35 years of holding it back, not talking about it, not exposing the real situation and in as such I've had to suffer a very long time."

The man, now in his 40s, credited the police investigator who had provided reassurance in believing his claims against Cooper, and had told him he had the full support of police.

He was hopeful Thursday's ruling would provide closure.

"The good thing about this is the exposure gives, hopefully, other people the lead to step forward. Just tell the truth," he said. "If more people could truly believe that I think it's a platform for this sort of hideous behaviour to be exposed."

Judge O'Neill found there were aggravating features in Cooper's offending, because he was "in a position of trust within the (brothers') family, and his conduct was a blatant breach of that trust".

He found Cooper groomed and manipulated a vulnerable teen, and rejected any suggestion his victim was in any way culpable because he failed to report the offending.

Sentencing judge Stephen Norrish said in 2013 Cooper had rightly "suffered a spectacular fall from grace" and had lost his status and occupation. But he found Cooper was remorseful, had been an "unblemished" character since the offending and would have been at risk in prison given his past roles as a prosecutor and magistrate.

His victim on Thursday revealed Cooper had pleaded for forgiveness in a meeting before charges were laid, but had never apologised.

Cooper was not in court on Thursday. Judge O'Neill reserved a decision on the man's application that Cooper pay more than $7000 in legal costs.