Niece killer gets more jail for sex crimes

A Sydney murderer will serve more jail time for his "horrendous" sadistic crimes which involved filming his sobbing, bound and gagged niece as he raped and taunted her.

Derek Barrett was jailed for at least 34 years and six months in 2017 after admitting stabbing Mengmei Leng, whose naked body was found floating in a NSW blowhole on the Central Coast in April 2016.

He was subsequently charged with a string of sex offences after videos of him sexually assaulting Ms Leng were discovered on a USB, mysteriously found in the hand of a woman with dementia in November 2019.

"These horrendous crimes can only properly be regarded as amongst the most serious examples of such offences that the courts have seen or are likely to see," Justice Helen Wilson said in the NSW Supreme Court on Thursday.

"Ms Leng's personal integrity was cruelly defiled by an offender who took pleasure in hurting, humiliating and degrading her.

"The offender manipulated Ms Leng's body as if she were a worthless inanimate object, and treated her with the most callous and injurious contempt."

The 32-year-old pleaded guilty to nine charges of assault with acts of indecency and aggravated sex assault, committed on April 22 2016, before he stabbed the 25-year-old niece of his wife at least 30 times.

The judge sentenced him to a further 20 years with a non-parole period of 12 years.

Most of the term is to be served at the same time as the murder sentence, but his new earliest release date is now two years later, in October 2052.

"Too frequently men - and it is almost always men - treat women as no more than an object to be used for sexual gratification, disregarding the rights of women to personal integrity and choice," the judge said.

"The offender must serve as an example to others that this attitude is very wrong, and crime that occurs as a consequence of it will be severely punished.

"Having regard to the offender's sadism, specific deterrence must also weigh heavily into the mix."

Each assault was committed when Ms Leng was fully exposed, bound and gagged.

"The assaults took place over a prolonged period, despite Ms Leng's attempts to fight the offender off and struggle against him; despite her pleas, tears, and cries of pain; despite her visible distress, her pain, and the bleeding from her genital or anal area," the judge said.

"This horror had clearly been planned, as had the offender's conduct in recording what he did for his later pleasure."

If he had been sentenced for the murder and the sex crimes at the same time, the judge said he would have received a life sentence.

"As he did when facing sentence in 2017, the offender has sought to distance himself from his crimes by blaming their commission on his use of drugs,'

But Justice Wilson rejected his claims he was in a drug-induced haze when he raped and filmed Ms Leng, had little memory of it and had previously been in a consensual sexual relationship with her.

"There should be no surprise that a man who would do what this offender did to another person would also lie about it,"

She also rejected a submission that Barrett had shown genuine remorse in a letter of apology to the victim's heartbroken mother.

In her translated victim impact statement, Tam Mei Zhang, asked the judge to sentence "this vicious rapist, malicious torturer and cold-hearted murderer, to life imprisonment".