On Tuesday, a man aged in his late 20s was sentenced to jail in Orange District Court for the aggravated sexual assault of a person who was under 16, and for an additional charge of sexual touching.

The offender is not named due to a non-publication order to conceal the identity of the victim.

The court heard the girl was drinking alcohol with the man and other people at a house in May, 2019.

Later that night, she went to sleep in a bedroom. However, the man came into the room, removed her shorts and sexually assaulted her. He then heard a noise outside the bedroom so he walked into the hall where he was confronted by his now ex-girlfriend, who found the teenager still half-naked but covering herself with a blanket.

It is understood the assault lasted less than a minute before the man left the room.

The man told his partner he thought the teenager was her, which the woman rejected due to differences in body shape. The partner then armed herself with a knife and curtain rod and assaulted the man causing cuts to his wrist and face.

Police later found his blood at the scene and he was treated by paramedics when he was arrested.

Another woman phoned police, and the man's partner took the girl to a female family member's house and a group of women drove the girl to the local hospital. She was transferred to Orange Hospital for a sexual assault assessment.

The court heard the victim has suffered as a result of the assault and coronavirus restrictions has affected her ability to see a counsellor.

At the time of the offence, the man was under the influence of alcohol, cocaine and cannabis. He said he had a history of drug abuse and drank whatever alcohol he could get including cask wine and rum straight from the bottle.

However, his drinking and drug use has been curtailed by the almost one-year and five-months he has already spent in protective custody in jail while awaiting sentencing. Orange District Court Judge Graham Turnbull said jail visitation was cut due to COVID-19 and as a result less drugs have been getting into jails.

Judge Turnbull said he considered the man's prospects of re-offending with sexual offences to be very low, but he was guarded when it came to prospects of further alcohol-related offending.

"He's certainly learnt his lesson, no doubt about that," Judge Turnbull said. "He's alienated from his family."

"I do note that this young person [the victim] is entitled to feel safe in [the] home, I do note she was asleep and more vulnerable in that way."

Judge Turnbull noted the man's scars from the assault and said it could be considered extra-curial punishment. He also noted that the man admitted the offence soon after it was committed.

He took into account that the man was exposed to alcohol abuse and violence when he was a child and he also took into account the man's cognitive impairment as detailed in a report, and a potential for a diagnosis for foetal alcohol syndrome.

"I do note that this young person [the victim] is entitled to feel safe in [the] home, I do note she was asleep and more vulnerable in that way" Judge Turnbull said.

Judge Turnbull also accepted the man's contrition, remorse and an early guilty plea.

"It's the biggest mistake of my life, I don't want this," the man was quoted as saying by a report writer.

"It's not suggested for one second that he tried to overbear the victim or to prevent her from leaving or getting help," Judge Turnbull said.

"It puts this matter completely in the low range of objective seriousness. [However], there's no other option but to impose a term of full-time custody."

Judge Turnbull gave the man a total jail sentence of three-years and four-months with a non-parole period of one-year and eight-months.

The jail sentence was back-dated to when he went into custody and he will be eligible to apply for parole on January 24, 2021. His overall sentence will expire on September 24, 2022.