Paedophile priest ruined young lives, court hears.

A Wentworth Falls priest was allowed to be moved to other parishes, despite the then Cardinal of the Sydney archdiocese and a high-ranking bishop knowing he had sexually abused a young boy, a court has heard.

One of the victims of Fr Robert Flaherty told a sentencing hearing at the Downing Centre on Friday how the assault had ruined his life.

Priest Robert Flaherty

Priest Robert Flaherty

"I heard the names of these so-called leaders during the trial, namely Cardinal James Freeman and Bishop Edward Kelly," he said. "I never had any contact with them but their decisions have impacted on my life.

"[They] knew that he had sexually abused a young boy and all they did was move him from parish to parish to give him new young boys to manipulate and abuse without having any restraints put on him.”

Flaherty, 72, showed no reaction as the man, once an altar boy, read his victim impact statement. 

Flaherty had pleaded guilty to three offences of indecent assault but was also found guilty by a jury of two similar offences.

Some of the offences took place at the priest's Mollymook weekender where he allowed the victim's sister to sleep in his bed in case any of the boys made advances towards her. He, instead, slept in the boys' room. That was something that took "a degree of planning and was something that was arranged", prosecuting counsel Mitchell Paish said.

The assaults took place during the 1970s but Flaherty was only arrested in 2013 after a third victim complained to police.

Flaherty held positions at churches in St Marys, Blacktown, Guildford, Woy Woy, Auburn and Richmond.

Mr Paish said that Flaherty should receive a full custodial sentence.

"Even now this man fails to realise the hurt and misery he has caused long term in people's lives," he said.

Defence counsel Leah Rowan said a doctor has said Flaherty, reportedly suffering from dementia, depression and diabetes, had only six to 12 months to live and a custodial sentence would hasten his demise.

"That in my submission means that any full-time custodial sentence your honour may impose would almost certainly be a death sentence," she said.

Judge Richard Cogswell interjected, saying: "Or a life sentence."

Flaherty will be sentenced tomorrow.​