"She's just amazing," he said. "Her survival instinct and the way she thought ... that's a real inspiration to other women out there. That's a great story."
Miss Montgomerie had been living with Boulter in Invercargill, but moved back to the island after he assaulted her.
Despite being on bail and being ordered not to contact his victim, Boulter tracked her down. On Great Barrier Island he told Miss Montgomerie he would kill her and that he had already killed her 7-year-old brother. He said he would kill himself and make her watch.
But, despite being covered in blood and bruises, reeling from multiple blows to the head and face and after passing out from being strangled, Miss Montgomerie convinced her attacker she was on his side.
She told him she wanted to walk to the wharf with him so they could "escape" together.
As they walked she persuaded him to throw the thistle grubber he was carrying as a weapon into a stream. For several hours she walked with him along a pig hunting track - barefoot and wearing her pyjamas.
She could hear searchers calling her name but was too terrified to answer.
She was also unable to cry for help as Boulter had severely damaged her throat when he strangled her with a shirt, rendering her unconscious. But she stuck to the charade, desperate to stay alive.
Her efforts paid off when a search team saw the pair running across a paddock.
During the sentencing yesterday, Boulter showed little emotion when Miss Montgomerie read a statement to the court.
"I thought I was going to die," she said. "I thought by leaving him it would mean that I was safe from him ... the long-term effects are probably the most painful for me."
She suffered from chronic depression and turned to alcohol - drinking a box of beer to put herself to sleep became routine.
"But I realised that wasn't going to help me and I had to stop."
Scars, ongoing treatment and panic attacks were a "horrible reminder" for her.
Miss Montgomerie also felt guilty over Boulter's attack on her new boyfriend, Michael Stewart.
On January 20 last year, the couple had just gone to bed when Boulter, who had earlier broken in and was hiding under her bed, emerged and attacked Mr Stewart.
As Miss Montgomerie screamed for him to stop, Boulter turned on her, kneeing her in the face and hanging her off a balcony by her hair and leg before dragging her away.
Boulter unmoved by victim's statement
For most of his sentencing, Nathan Boulter sat stony-faced. Unmoved while his victim read a harrowing statement to the court. Unemotional as lawyers debated his mental illness and what impact it had on his offending.
He did not flinch as Justice Paul Heath described his lack of empathy and understanding of what he had put his victim through and the aftermath.
It was not until details of his "unusual" past were revealed to the court for the first time that Boulter showed a glimmer of feeling.
His lawyer, Paul Gruar, told the court that Boulter was born and raised in Southland in a loving and supportive family. He never met his biological dad but was close to his stepfather, considering him a "true" parent.
But at 13 his behaviour began to deteriorate after he was sexually abused by "someone who lived near the family home". His mother could not handle his behaviour and he was shuffled, he told a court-appointed psychologist, between 57 Child, Youth and Family foster homes over a three-year period.
Mr Gruar said Boulter had anger management problems, a low tolerance for frustration and was prone to outbursts. His sister was diagnosed with schizophrenia and Boulter was said to have a "genetic vulnerability" to mental illness.
After forming a relationship with Nortessa Montgomerie and moving with her back to Invercargill, his need for medication was identified.
But he "could not afford" the prescription so his pills were "discontinued abruptly".
It was this, Mr Gruar said, that contributed to another deterioration in behaviour.
"He had constantly announced to his family his frustration and disappointment with his life," the lawyer said. "The breakdown of his relationship [with Miss Montgomerie] was extremely serious in terms of his deterioration."
He regularly threatened self-harm and his mother asked him to leave her home.
"He then embarked on this tragic series of events ... there is a cause and link between his mental state at the time of the offending and the events that took place."
Pre-sentencing reports stated that Boulter displayed symptoms of a psychotic illness - but the link between those and the crime was "tenuous".
Mr Gruar said what Boulter did was "bizarre and highly unusual". He had planned a "one-way" trip north, intending to take his own life.
"But he went further than harming himself."
Justice Heath described the crime as "horrific".
