Three Goulburn detectives made up Strikeforce Charish, formed in February, 2014 to investigate allegations of child sex offences said to have occurred between 1978 and 1990 at the former St Patrick's College.

Detective Senior Constable David Turner, Detective Sergeant Matt Woods and Detective Senior Constable Mick Calleja have investigated allegations against three Christian Brothers who taught at the Catholic School.

On Friday, one of them, Brother William Peter (known as David) Standen was sentenced in Sydney District Court to nine years, two months' prison with a non-parole period of four years, seven months.

He had pleaded guilty to 17 charges of indecent assault of boys aged 12 to 14, and one act of indecency on a boy, while he was at the College from 1978 to 1981.

Victims have praised the detectives' work and that of the prosecution team. On Friday afternoon they gathered for a debrief with prosecutors following the hearing.

DSC Turner was at the court for the sentencing.

He described it as an extensive inquiry which started in February, 2014 with one complaint.

"Our initial inquiries had led us to believe there were more," he told the Post. "Inquiries and investigations eventually led to 18 victims all around the State."

DSC Turner said it was a time consuming exercise identifying victims, gathering evidence and statements.

"It was a big relief when he (Standen) pleaded guilty," he said.

"The victims showed a lot of courage and I'm happy with the result today. Hopefully it will give them (victims) some closure and enable them to get on with their life."

Hume Local Area Command crime manager Detective Inspector Chad Gillies gave credit to the team.

"In particular, the leadership and efforts of Detective Senior Constable Dave Turner ought to be recognised and I formally recognise him today," he said.

Another Christian Brother, who also taught at St Pat's, William John Obbens, 70, will be sentenced in Sydney District Court on June 20.

Last month in Goulburn District Court he pleaded guilty to three counts of aggravated indecent assault of three children under 16 under his authority.

The charges relate to his time as a teacher and dormitory master at the school from 1987 to 1989.

Brother Christopher Rafferty, an ex-St Pat's teacher, was also charged under Strike Force Charish.

The 63-year-old is yet to plead on two counts each of indecent assault on a male, two charges of sexual assault and commit act of indecency, three counts of homosexual intercourse with a pupil and one of sexual assault and indecent act on a child aged 14 to 16.

He will face trial in Sydney District Court on August 15.