A MAN who murdered his niece before dumping her body in a blowhole has told a Sydney court of his self disgust following his violent, sexually motivated crimes.

Derek Barrett, 29, previously pleaded guilty to the stabbing murder of Chinese university student Mengmei Leng, whose naked body was found floating face down inside the blowhole at Snapper Point on the NSW Central Coast on April 24, 2016.

He also pleaded guilty to another 21 offences relating to the filming of Ms Leng for sexual gratification.

Ms Leng, 25, had lived with Barrett and her aunt in the southwest Sydney suburb of Campsie since arriving in Australia to study five years before her murder.

“I betrayed my own family and hers for my actions,” Barrett said at the NSW Supreme Court on Wednesday during his sentencing hearing.

“I disgust myself.” Barrett admitted he was sexually attracted to Ms Leng.

“She was a pretty girl,” he said.

According to agreed facts, Barrett gagged and bound Ms Leng to her bed in the early hours of April 22 while his wife away.

He then took 19 photos of her naked body.

At some point over the next two days, Barrett stabbed Ms Leng multiple times, inflicting a fatal stab wound to the throat.

On the morning of April 24, he drove her body, wrapped in plastic, to Snapper Point and dumped it over a cliff into the blowhole.

The former IT worker then took seven photos of the area before driving to his parents’ house nearby and later returning to Sydney.

Barrett told the court he only has flashes of memory from that weekend - an argument, his face reflected in the mirror and seeing blood in the sink. He said he’d been on an ice binge before killing Ms Leng, which affected his memory.

He admitted initially lying to police because he “couldn’t figure out what exactly happened until a little later.”

“With the memory gaps I basically filled them in with lies,” he said. The sentence hearing continues.