Former Bishop of Broome Christopher Alan Saunders, 76, was found guilty of 13 sex offences on Thursday following a jury trial in the West Australian District Court.
The offending between 2008 and 2019 included one count of sexual penetration without consent and a dozen unlawful and indecent assault charges.
He was acquitted of six other charges, including two counts of indecently dealing with a child over 16 under his authority and four counts of unlawful and indecent assault.
Saunders was ordained as the second Broome bishop in 1996 and presided over 13 schools and nine parishes, before stepping aside in 2020 when the sex abuse claims became public.
Pope Francis accepted his resignation a year later.
Unless acquitted on appeal, Saunders would be the highest-ranking Catholic in Australia convicted of sexual abuse while a member of the clergy.
The late Cardinal George Pell was found guilty in 2018 but later acquitted by the High Court of raping one choirboy and molesting another in 1996.
Prosecutors said Saunders, known as Brother B by his victims, put on alcohol-fuelled parties at Catholic Church-owned properties to get access to Aboriginal boys and men so he could sexually assault them.
"The accused had a sexual interest in young Aboriginal men and a tendency to act on that interest when the opportunity presented itself," prosecutor Adam Ebell said.
Saunders, who studied law before becoming the first diocesan priest ordained in WA's Kimberley region in 1976, exploited the power imbalance between himself and the younger men, he said.
The main complainant, who cannot be named for legal reasons, said he was aged 16 when the then-bishop started grooming him at a Broome home in regular visits during which he was given alcohol.
The interactions over the decade that followed involved kissing, naked wrestling, touching of private areas and penetrative sex, he said.
Saunders denied the sexual assaults took place.
His lawyer Tony Hager attacked the three complainants, saying they were convicted criminals with long records who had abused alcohol and drugs during their lives which impacted their memories.
Saunders was initially on trial for 30 sexual assault charges, but four charges related to a child under the age of 13 were removed from the prosecution on the first day of proceedings.
He was acquitted of a further seven charges mid-trial due to insufficient evidence being presented to the jury.
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