A former IT worker behind bars for repeatedly stabbing his niece whose naked body was found floating in a NSW blowhole is facing sentence for a string of sex offences.
Derek Barrett, now 31, was jailed for at least 34 years and six months in 2017 after pleading guilty to murdering student Mengmei Leng, whose body was found in the blowhole at Snapper Point on the Central Coast in April 2016.
He had admitted filming the 25-year-old niece of his wife, while she was bound and naked, for his sexual gratification.
"This was a despicable crime of extreme brutality and great wickedness," Justice Helen Wilson said when jailing him for a maximum of 46 years in the NSW Supreme Court.
Barrett appeared via video link in the same court on Friday after pleading guilty in a local court to numerous counts of assault with acts of indecency and aggravated sex assault, depriving liberty.
Justice Robert Allan Hulme sent the case back to Justice Wilson for a sentence hearing on December 9.
She had described the murder as "a depraved and sadistic act committed by a man in a position of trust to Ms Leng and in a place that should have been one of safety and refuge for her".
Ms Leng had lived with Barrett, her aunt and her cousin in the southwest Sydney suburb of Campsie since arriving in Australia in 2011 to study.
When his wife was out of town Barrett gagged and bound Ms Leng to her bed. He then took 19 photos of her naked body.
Justice Wilson said Ms Leng must have been in great pain and fear as she lay "humiliatingly exposed".
In one photo the student "appears terrified", she said.
At some point over the next two days, Barrett stabbed Ms Leng at least 30 times, inflicting a fatal stab wound to the throat.
He drove her body, wrapped in plastic, to Snapper Point and dumped it over a cliff into the blowhole.