The ACT Supreme Court last September sentenced the offender to a 23-month term with an 18-month non-parole period after he pleaded guilty to committing an act of indecency on a child.

Agreed facts state the man was living in Canberra's north with his then-partner, a child of their own and his stepdaughter, six at the time, when the offence occurred in the latter's bedroom in April 2021.

While he was supposed to be looking after the girl, who called him "daddy", the man took off the girl's pants and underwear.

The 40-year-old man then touched the girl's vagina for about 20 seconds.

That night, the victim told her mother, who then confronted the offender with the allegation.

He admitted touching his stepdaughter inappropriately but denied doing it on purpose and said it had happened while he and the girl were "mucking around".

The girl's mother called the police almost immediately.

When officers spoke to the man the next day, he told them the girl had refused to stop using her iPad when "screen time" was over.

He said he resorted to "roughhousing", and touched girl's vagina for about 20 seconds to get a reaction from her.

Sentencing judge, then acting Justice Verity McWilliam, rejected his claim, saying there was "simply no context" in which "roughhousing" would create a need to remove the girl's pants and underwear.

"The only reasonable inference for the court to draw from the offender's conduct is that it was done for sexual gratification," she said.

MORE COURT AND CRIME NEWS

Among the offender's grounds of appeal, filed last November, were that the sentencing judge did not apply the appropriate discount for an early guilty plea and the judge incorrectly considered the strength of the prosecution case in determining the discount for that plea.

Other grounds were that the non-parole period was excessive, the judge failed to provide sufficient reasons in determining that period, and the overall sentence was manifestly excessive.

The ACT Court of Appeal on Tuesday found the sentencing judge erred in considering the strength of the prosecution case when assessing the discount for the offender's plea of guilty despite no submission being made about the prosecution case being overwhelmingly strong.

Justice Loukas-Karlsson, one of the appeal court's judges, said it was worth noting that taking into account the strength of the prosecution case would create significant difficulty for the predictability and consistency in guilty plea discounts.

"Especially as pleas entered at an early stage may be made well before the full strength of a prosecution case becomes apparent," Justice Loukas-Karlsson said.

"Such an approach would therefore discourage offenders from pleading guilty and would not have been the intention of the legislature."

Justice Loukas-Karlsson said it "is clear from the victim impact statements that the offending has had a significant impact on the victim and the victim's mother".

"In relation to the offender's attitude towards his offending, I note that the offender has engaged with a counselling program as outlined above and made admissions and apologies concerning the offending," she said.

"Nevertheless, I note that the pre-sentence report indicated that the offender did not 'seem to understand what other ramifications his actions may have had on his victim'."

The offender was re-sentenced to 21 months' jail to end in June 2023, with a non-parole period of 13 months ending this October.

The error in considering the strength of the prosecution case meant the appeal court did not need to consider the other grounds.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: