And Michael Alan Gillard now faces another sentence for sex crimes against the victim's little sister.

Chief Justice Terence Higgins sentenced Gillard to nine years and nine months for ''an egregious act of betrayal'' towards adolescent girls in his care.

In a victim impact statement read in the ACT Supreme Court yesterday, his older victim described how Gillard ''took my childhood, my innocence and my freedom''.

The woman added ''he no longer has, and never will have, control over me.

''I believe the world will be a safer place if he loses his freedom and never has the chance to do to another child what he did to me.''

But the court heard Gillard is set to appeal against at least some of the convictions.

Earlier this year a jury found Gillard guilty of eight sexual offences, all but one - committing an act of indecency in the presence of another - against the older girl.

The exception was an incident when he forced the girl to give him oral sex as the younger girl looked on in shock.

The sentencing judge described that particular offence as Gillard demonstrating his power over his victim.

He was also found guilty of possessing child pornography in relation to nude photos taken of the older girl.

And earlier this week, after a separate trial, a jury convicted him on charges of having sex with the younger girl, then just 13, and committing an act of indecency on her.

The 57-year-old faces a sentencing hearing before Justice John Burns in relation to the second trial next week.

The abuse of both victims occurred between 1995 and 2000, when the girls would come to stay with Gillard in Canberra during the school holidays.

Their brother was ill and confined to a hospice in the capital so Gillard, a friend of their father's, arranged to take them into his care so they could be closer to the sick man. ''I think he had, in his own twisted mind, [the impression] that she fancied him,'' Chief Justice Higgins said in relation to the older victim.

He added ''nothing could be further from the truth''.

Defence barrister Ken Archer pointed to his client's lack of relevant convictions, and argued Gillard was a good candidate for rehabilitation.

But prosecutor Margaret Jones said it wasn't unusual for child-sex offenders to have an unblemished criminal record.

''The accused took advantage of [their] situation, he had them in his care, they were a captive audience ... there was nowhere they could go, there was no where they could turn,'' Ms Jones said.

The judge said the most important factor in sentencing, ''regrettably, is punishment''.

''He was in a position of trust in respect of her,'' Chief Justice Higgins said.

''He knew she, and her sister for that matter, were in his care because of the tragic circumstances which concerned their older brother.''

The prisoner will be eligible for parole in March 2017.