Court documents provided to Open Justice have revealed more details about the case, including Duncan's upbringing in and out of state care, blighted by physical and sexual violence and by complicated psychological issues brought about by deprivation and abuse.
This background, along with his gang involvement and substance abuse, led Duncan along a pathway of offending and prison time, with convictions for burglary, robbery, aggravated robbery, common assault and assault with intent to injure.
By the age of 25, he had received two strikes under the now-repealed "three strikes" legislation.
However, until last year, Duncan's offending history had been violent but not sexual.
That changed three months before the home invasion, when he attempted to sexually violate a young mother in an unrelated attack, with an associate, after entering that woman's house. She fought him off when her baby started crying.
Duncan was on bail for that offence when he attacked the elderly woman, who he did not know, after breaking into her home seemingly at random.
The victim's "wonderful life (was) destroyed by one atrocious event", according to her son. Duncan terrorised her for about an hour.
The son was the third of Duncan's victims.
He had gone to check on his mother after missing calls from her phone, and found Duncan attacking her.
He confronted Duncan – bravely, a judge said – but was punched, strangled and kicked unconscious.
During the attack, the elderly woman managed to push her St John alarm, connecting her by voice to an ambulance control room.
Duncan calmly told St John that she was his mother and the call was made in error.
However, St John sent two officers after the alarm was pushed a second time. When they arrived at the house, Duncan walked past them, calmly saying, "It's okay, she's asleep in her bedroom".
They noticed he had a knife in his hand.
After the attack, Duncan went to a dairy and calmly ordered a pie before catching a taxi.
In a written submission to the High Court sentencing judge, Justice David Gendall, Napier Crown solicitor Steve Manning noted a comment that Duncan had made to a psychologist who interviewed him after the attack.
He told the psychologist he was going to kill his victim, but was interrupted when the paramedics arrived.
Duncan appeared in the High Court at Napier after pleading guilty to multiple charges against his three victims including rape, sexual violation, attempted sexual violation, assault with intent to commit sexual violation, aggravated injury, grievous bodily harm, threatening to kill, and three burglaries.
Several reports were written about Duncan when he was waiting to be sentenced. They include two psychological assessments, a psychiatrist's report, a probation officer's pre-sentence report, and a report on personal and cultural circumstances.
The pre-sentence report described his upbringing as "rough" and dysfunctional, and assessed him as having a high risk of reoffending.
It said the death of his father in 2018 was "impactful" and Duncan was highly dependent on alcohol, methamphetamine and other drugs before committing the latest offences.
A psychologist's report noted Duncan had suffered regular physical and sexual abuse growing up, along with threats of violence from his mother, and a lack of schooling.
"Overall," said Justice Gendall, "the report discloses … that you encountered negative and traumatic experiences throughout your childhood that resulted in you pursuing an antisocial and gang-entrenched lifestyle."
The psychiatrist's report revealed that Duncan was the victim of sexual abuse while in care at a boy's home, Justice Gendall said.
He never received counselling.
Crown Solicitor Manning argued without success for the open-ended jail sentence of preventive detention, arguing that Duncan had been subject to all manner of sentences, including imprisonment, over 10 years and they did not prove a deterrent.
Duncan had made little effort to address the causes of his offending and the latest offending happened only six months after he was released from prison, he said.
Manning said Duncan was likely to offend again.
"The defendant's offending was so extreme that it is indicative of someone who has deep-seated issues that drive his criminal behaviour," Manning said in his submissions to the sentencing judge.
"Those issues will not be removed, or even mitigated, without a considerable amount of rehabilitation."
Manning said Duncan's history suggested he was unlikely to engage with the rehabilitation he needed.
SEXUAL HARM
Where to get help:
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone, contact
Safe to Talk
confidentially, any time 24/7:
• Call 0800 044 334
• Text 4334
• Email support@safetotalk.nz
• For more info or to web chat visit
safetotalk.nz
Alternatively contact your local police station -
click here for a list.
If you have been sexually assaulted, remember it's not your fault.
