A former WA youth worker and foster carer who sexually abused three boys will spend at least eight years behind bars.

A former West Australian youth worker and foster carer who sexually assaulted three teenage boys more than 20 years ago has been jailed for 10 years.

Roderick Alexander Finch, 55, pleaded guilty to 21 child sex offences including indecent dealings with a child, sexual penetration of a child and attempted sexual penetration of a child.

The Perth District Court heard on Friday that Finch was the foster carer for two boys – one of whom had “special needs” – whom he plied with alcohol before abusing.

The third victim, a 16-year-old boy, was a juvenile offender who was abused while doing community work at a camp.

In sentencing, Judge Felicity Davis said it was regrettable that Finch moved to Queensland in the 1990s and was not charged then despite one of the boys alerting police.

Judge Davis said the boys were vulnerable and there was an element of forceful or coercive behaviour as Finch invaded the safety of their beds for his own sexual gratification.

“You were in a position of trust and authority for these children,” she said.

“You abused that trust in one of the worst possibly ways.”

Judge Davis said the victims had suffered long-term effects including mental health problems and isolated lives.

She also outlined Finch’s own troubled past involving a fatal car accident in which he was the driver, alcoholism, a conviction of possessing child pornography, and health issues including two strokes.

Judge Davis accepted that Finch was remorseful and was a low to moderate risk of re-offending.

“You also recognise that your offending has destroyed the lives of these complainants,” she said.

In an earlier letter to his lawyer, Finch admitted his guilt saying: “I had the chance to help these kids and I didn’t help them at all – I damaged them.”

He must serve eight years before being eligible for parole.

Outside court, victim Rob McAuley said he was happy with the sentence but had hoped for at least 15 years.

“It’s over, it’s finished. Now I can move on,” he said.

But Mr McAuley said he did not accept Finch’s remorse and said he was still dealing with long-term effects of the abuse.

“I’ve never really had a relationship long-term,” he said.

“I haven’t really been able to hold down jobs.”