Jaden Lee Stroobant has been sentenced to preventive detention and life imprisonment with a minimum non-parole period of 17 years for the rape and murder of 69-year-old Cun Xiu Tian.
Stroobant chewed gum throughout the hearing and was fidgety in the dock at Auckland's High Court.
He had been released from prison 38 days before the attack and had been visiting his mother who lived next door to Cun Xiu Tian in Glenvil Ln, Te Atatu when he attacked.
In January 2016, while Ms Tian was gardening, Stroobant hit her around the head and stomped on her face.
While she lay dying from those injuries, he sexually assaulted her and stole an Ipad, $370-worth of Chinese Yuan and a gold watch.
In a victim impact statement read to the court, Ms Tian's son-in-law said he suffers "a lifetime of fear, insomnia, panic attacks, anger and first-hand knowledge of how deeply depraved and disgusting a human being can be".
Ms Tian's daughter explained that Ms Tian had previously recovered from cancer. She spoke of the day she realised her mother had been attacked, saying: "I cannot imagine the pain my mum suffered."
"We are ordinary people, powerless. Life has been turned upside down in the blink of an eye.
"My heart was shattered - I can't believe he is a human being.
"I felt such guilt for not being there when mum needed me."
The trial had been due to start in February this year but Stroobant pleaded guilty on the opening day.
In sentencing, Justice Lang said the offending "helps to destroy the very social fabric of our community".
He said the attack happened in broad daylight when "people should feel entitled to feel safe in their own homes".
Stroobant's aunt, Renae Stroobant, was in court to hear the sentencing and mouthed "hey baby" when he entered the courtroom. Defence lawyer, Emma Priest, explained to the court his aunt had been the most stable figure in his life.
At this point there was some tense discussion between his aunt and mother, Krissie Stroobant, who was also present.
Ms Priest told the court Stroobant "comes from a severely dysfunctional family" - having been in a violent relationship in the home with his mother, stepfather and siblings.
Renae Stroobant has previously been jailed for possessing precursor substances for the manufacture of methamphetamine, possession of utensils for manufacture and allowing her home to be used to make the drug. This came at a time when Renae Stroobant was speaking publicly as a campaigner against the dangers of 'P'.
The Crown prosecutor revealed Jaden Lee Stroobant has been sentenced four times previously to crimes that have put him in jail more often than not since he was 17 years old.
He had attended special schools and had hundreds of hours of psychological support to address his educational needs but had been expelled for a series of incidents where he punched teachers. From the age of 14 he embarked on a career of burglary.
A psychological report into the likelihood of his risk of future violence found he was in the 100th percentile for lack of remorse, grandiosity and manipulative behaviours.
Tensions boiled over in January 2016 when Stroobant appeared at the Waitakere District Court.
He yelled and swore in the court, and those in the public gallery screamed abuse back at him.
"Today marks the end of an appalling case," Detective Senior Sergeant Roger Hall said outside the court on Friday.
"Many of our officers, some who have been in the police for many years, were shocked, appalled and upset by the extreme violence suffered by Madame Tian.
"We would like to acknowledge the ongoing grief and thank them for the faith that they showed throughout the entire investigation."
Ms Tian's daughter and son-in-law were satisfied justice had been served, Detective Sarah Cato said.
"Christina and Jerry would like you all to know how grateful they are for the sentence handed out today.
"They are appreciative of the amazing work and support provided to them by the New Zealand Police, the Crown, community groups, their church and their friends. They could not have got through this terrible time without it."