When one boy reported William Stuart Houston, the head Brother declared: "This is what we do to boys who fabricate stories about us", and strapped the child every morning for five days in front of the entire St Augustine's orphanage.

That victim, now in his 60s, told the County Court on Thursday of the anger that still consumed him at being accused of lying and punished by the two Brothers he had approached separately about Houston.

"I am still angry to this day and the anger will be there because as a ward of the state I was let down by the system. I will never forgive William Houston for what he did to me," he said. The court heard another victim was also punished after reporting Houston.

Houston, 77, was last month found guilty at trial of four charges of buggery, one of attempted buggery and three of indecent assault, related to attacks on three boys at the Geelong orphanage in the 1960s.

He was to face three more trials, but on Thursday pleaded guilty to 12 charges of indecent assault, related to assaults on three other boys.

No longer a Christian Brother, Houston has been investigated by police before, but was never convicted. He is now in custody awaiting sentence for his attacks on six boys, aged between 10 and 14.

Prosecutor Ray Gibson said Houston preyed on vulnerable boys in his care, often abusing them while they were in their beds. The effects of the prolonged offending had been profound given the serious breach of trust.

After abusing one boy, Houston told him: "Don't tell anyone. That's right, you can't tell anyone because you've got no one."

The victim strapped in front of his peers told the court of the "short fuse" he developed at being regularly abused for at least a year, for not being believed and at being told to fend for himself when he turned 16.

The anger inside him had affected his marriage, family relationships and friendships. "I became a violent, angry drunk," he said.

Another man spoke of nightmares he still endured that were so violent that during one he fell out of bed and cut open his head.

Another told the court he could still recall Houston's stubble and tongue on his face, while the court was told one man had suffered injuries but shame had prevented him from undergoing a mental examination.

Defence counsel David Hallowes said his client was in good health for a man of his age, but told chief judge Peter Kidd to be mindful that much of Houston's remaining years could be spent in prison.

"There is a potential he won't be released from jail," Mr Hallowes said.

Houston spent most of the hearing looking at the floor with his hands on the side of his face. He will be sentenced this month.