Kenneth Edward Hill, 35, is already serving a three-year jail term for punching and sexually assaulting a prostitute.

Acting Justice David Robinson this month added an extra 14 months to the sentence, and extended the non-parole period by seven months. Hill will now be eligible for parole in March 2018.

The ACT Supreme Court heard Hill had a minor criminal history until he turned 30 in 2010, when he was convicted of assault and sentenced to a good behaviour order. But it was a series of sex offences last year that will see Hill behind bars until 2018 and subject to conditional liberty until 2020.

In April last year, Hill committed an act of indecency on a young girl as she walked home from school. He was sentenced to 18 months jail to start on August 21 last year.

It was while he was on bail for that offence that he accessed the child pornography and sexually assaulted a prostitute.

About a week before the sentence started, Hill made an appointment to see the sex worker at her unit. He arrived about 9.10pm and soon after struck the woman in the face, knocking her to the ground, and then sexually assaulted her. The victim fought back and Hill fled.

He later claimed to be under the influence of methylamphetamine at the time after his drink had been spiked.

A police raid on Hill's home on August 20 last year discovered he had accessed about 64 child pornography images from his mobile phone between May and July last year. Analysis showed the images fell into the low level category of seriousness.

Hill initially pleaded not guilty to one count of using a carriage service to access child pornography and was committed to stand trial. He switched his plea to guilty before the trial.

In September, Acting Justice Robinson sentenced Hill to three years jail, with a non-parole period of two years, for charges of sexual intercourse without consent and assault occasioning actual bodily harm for the attack on the sex worker.

Earlier this month, the judge extended the jail sentence, and ordered Hill sign a two-year good behaviour order upon his release and undertake an adult sex offender program.

During sentencing proceedings, the court heard that, about the time of the offences, Hill claimed he had been consuming about 50 grams of cannabis and drinking three litres of wine a day. He had participated in a program to address his drug and alcohol dependence while in custody.

A presentence report corroborated Hill's empathy for his victim, but the author also noted the offender accepted only limited responsibility for his actions and appeared to reduce his culpability on the basis of his claims that his drink had been spiked.

In handing down sentence, Acting Justice Robinson found Hill had shown some progress in rehabilitation while in prison.

"[But] his prospects of success must be still be regarded as uncertain," Acting Justice Robinson said.