In August 2017 Cooper was released from prison after serving a sentence for violent offending against the same woman.
The following month he was at a Moerewa house with the woman and struck her about the head then grabbed her hair and smashed her head through the hallway wall.
As she was suffering an asthma attack Cooper sat on top of her and head-butted her.
On another occasion the woman was in the passenger seat of a vehicle being driven by Cooper. He hit her round the legs and she tried to get out of the moving vehicle.
Cooper started punching her in the head before stopping the vehicle and dragging the woman out.
Cooper sat on the woman and put his hands round her throat causing her to pass out.
During another violent attack Cooper threw the woman into a tin fence, causing her leg to become stuck in the fence. Cooper then attacked the woman punching her in the head and torso.
In another attack the woman tried to seek refuge under a car but Cooper struck her on the head and, while being taken to a medical centre by a family member, she lost consciousness.
And as the violence continued Cooper consumed methamphetamine and attacked the woman using the butt of a rifle before putting the barrel of the gun into her mouth and with his finger on the trigger threatened to kill her.
In the last attack, 10 days before Cooper was arrested, the woman was beaten for three hours in which she lost and regained consciousness several times. Eventually she was taken to hospital by a friend. As a result of the attack, she suffered a subdural bleed, fractured lower back ribs, swelling to the front lobe of her brain, nose fracture, a tear to her lung, bleeding to both eyes and bruising over most of her body.
A report completed by a forensic psychiatrist considered Cooper's violence was extreme and in relation to the victim could escalate to a level which was life-threatening.
The report writer said Cooper had long standing psychological problems, resorted to violence and aggression, and struggled to regulate his feelings.
Justice Christine Gordon said the offending started immediately after Cooper was released from jail for a sentence of one year and two months' imprisonment for violent offending against the same woman.
At the time Cooper had release conditions which included not to contact the victim. There was also a protection order in force at the time.
"Violent offending, particularly domestic violence like this, has significant impact on the victims, as well as their families and the community," Justice Gordon said.
She was not satisfied a lengthy prison sentence would provide adequate protection for society and previously Cooper had been given the opportunity to address his offending but had refused or had been unsuccessful.
"In my view you represent a serious risk to the victim and the community should you be released."
She sentenced Cooper to preventive detention and ordered him to serve a minimum jail term of eight years and three months before he could go before the parole board.
Preventive detention is an indeterminate sentence allowing Corrections to have control over the offender and, if released on parole, recall him to prison at any time.
