Derek Barrett pleads guilty to sex assault of murder victim Mengmei Leng

A man jailed for murdering his niece, whose body was found in a blowhole, has admitted sex offences against her.

A Sydney man jailed over murdering his niece, whose body was found in a blowhole, has admitted to fresh sexual offences against her after a dementia patient was mysteriously found with a USB containing images of the attacks.

Derek Barrett, now 32, was sentenced to a minimum 34 years jail three years ago for bounding his niece Mengmei Leng, 25, at his Campsie home before fatally stabbing her in 2016.

Her body was later found floating in a blowhole at Snapper Point on the Central Coast.

International student Mengmei (Michelle) Leng.

The NSW Supreme Court was told on Wednesday that in November 2019 a woman arrived at her elderly mother’s Strathfield home and found her in the kitchen holding a USB in a “rather unusual set of circumstances”.

“The woman’s caring daughter came home and found her mother sitting in the kitchen and in her hands was a USB,” Crown prosecutor Huw Baker, SC, told the court.

“(The elderly mother was) unable to explain what was in her hand. Her daughter thought it was a toy. She discovered it was a USB and put it into a computer to see what it would contain.

“On that USB she saw video files and pornographic images and she was immediately concerned. She called police and police attended and took possession of the USB.”

Murderer Derek Barrett and his niece Mengmei Leng.

Detectives viewed the material and were able to match 10 images deleted from Barrett’s phone prior to his arrest over Mengmei’s death in 2016 to the USB, the court heard.

The court was told the new videos were of the detention and sexual assault of his victim.

Mr Baker said there was no explanation as to how the USB ended up in the hands of the elderly woman, who suffers from dementia and is usually housebound.

Barrett appeared in court on Wednesday and pleaded guilty to a string of fresh sexual assault charges over the material on the newly discovered USB, including assaulting Mengmei and immediately after committing an act of indecency.

After his arrest in 2016 he was no charged with her sexual assault. He was sentenced over her murder.

Derek Barrett is led into the supreme court.

Mengmei Leng on CCTV shopping in Sydney.

Forensic psychiatrist Dr Richard Furst told the court that Barrett had denied his own conscious awareness of his own deviance after his offending.

“(Taking) images of the victim gagged and bound with the look of horror prior to her death were actions highly suggestive of sexual deviance,” the psychiatrist said.

Dr Furst said Barrett had maintained an erection while binding and sexually assaulting Mengmei before ultimately killing her.

“The fact he was able to sustain an erection and achieve ejaculation … the average person would be repulsed,” he said.

The matter was adjourned to a later date.