A chaplain and a teacher, he officiated at school Masses, led the pupils in prayer and gave them religious guidance.
He also, according to allegations by 13 former students, repeatedly sexually assaulted them.
One alleged victim, who completed year 7 at the well-known Catholic boarding school in 1986 before being expelled, blew the whistle on 65-year-old Spillane's alleged sex offences.
He was also a key witness in the conviction of a former St Stanislaus science teacher, Steven Joseph Wade, who was jailed in 2002 for sex offences committed at the school in 1986.
The allegations of sexual abuse are only the latest in a string of abuse scandals to fuel public debate about the Catholic Church and the conduct of its clergy.
The school says it first became aware of the allegations against Spillane five years ago, when it was contacted by the same alleged victim. It forwarded the allegations to Bathurst police, who sent the information to the child protection and sex crimes squad.
What became of that investigation is unknown but in August last year Bathurst police set up Strike Force Heador to investigate the claims of abuse by Spillane and two other staff members.
The investigation was a watershed for the original whistleblower, who has been diagnosed with post-traumatic stress disorder and has spent time in psychiatric care.
Four more former pupils came forward to allege abuse and in May police charged Spillane with 33 offences.
The charges included six counts of sexual intercourse with pupils aged 11, 12 and 13, and 18 counts of engaging in and inciting acts ofgross indecency. The other charges related to sex with males aged between 10 and 16.
Early last month police executed search warrants at the school in relation to two former priests and a lay teacher; one is understood to be Spillane and another Wade.
Yesterday Spillane's lawyer, Greg Walsh, declared his client's innocence.
Since the charges were laid another eight pupils have come forward to allege abuse and assault.
The principal of the school, John Edwards, said Spillane had joined the school in the 1970s, left, then returned in the mid-1980s, when he was school chaplain for a number of years. He left the school in 1991 or 1992 but remained a member of the congregation for some time.
He then worked at a Queensland parish before returning to Sydney and, as late as 2004, was serving at the Ashfield headquarters of the Vincentians, the order that runs St Stanislaus.
At a July hearing for his case, Spillane's lawyer stated he was no longer a priest and had married.
The recent charges have also renewed the concerns of some former St Stanislaus pupils who had long suspected something was not right.
One who attended about a decade before the whistleblower said he had observed late-night visits to priests' and brothers' quarters by pupils.
He had suspected a cover-up, he said, and once he heard about the charges levelled against Spillane he became more suspicious.
"I was suspicious when I was at Stannies. I'm more suspicious now about the boys going late at night to staff quarters. [There were] also outings we had - camping overnight in tents at places like Trunkey Creek."
The activities of priests and brothers should have been known to other staff members because they were obvious to students, he said.
The then college president, Joe Keady, died several years ago. The second-highest ranking priest was Father Peter Dwyer. He is a parish priest elsewhere in the state.
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