How a violent, possessive stalker became a killer

Thirteen years after being sentenced for kidnapping his ex-partner, holding her hostage for 38 hours on Great Barrier Island, Nathan Boulter stood in front of a judge in the High Court. This time he was pleading guilty to murdering a woman. RNZ's Sam Sherwood reveals how the violent, possessive stalker became a killer.

As Nortessa Montgomerie looked at her phone and read the news article, she felt nervous.

It was about a man sentenced for disorderly behaviour. He had made unwanted remarks to a young woman at a shop in Riverton and then challenged her father to a fight.

The offending itself was unlikely to make headlines - except for one crucial detail that left Nortessa on edge, fearful of what might come next.

The man in the dock was the same man she had feared for the past 15 years.

The man who in 2010 travelled the length of the country to find her after she fled their abusive relationship, hiding under her bed before attacking her.

He then dragged her into the bush on Great Barrier Island, holding her hostage for 38 hours while he continued his assault.

He was jailed for eight years and six months, but prison did little to change him.

About a year after his release, another woman, a friend of his sister's, became his target.

He became obsessed with her. She repeatedly asked him to leave her alone. He wouldn't.

He was jailed again for two years and five months.

While in prison he told a guard he was going to kill the woman once he got out, and sent her a letter in breach of a protection order.

By March 2023, he was back on parole with special conditions. He would offend again and be in and out of prison.

As Nortessa read about his latest offending, she was struck with fear. His behaviour was escalating. She was afraid of what he might do next, scared not just for her own wellbeing but for other women.

Then, 16 days after his release from prison, her fears became reality.

This time his victim was a mother with whom he had shared a very brief relationship.

"It is the worst case scenario," Nortessa says.

"It is everything that I wanted to stop from happening.

"How did it get to this… how did I see this but the people that were responsible for his care not see it?"

On Thursday the man, Nathan Boulter, pleaded guilty to murdering the woman, whose name is suppressed, allowing RNZ to reveal his full criminal history

Nortessa met Boulter in 2010 while she was living with her mother in Auckland.

After their shower window broke her mother contacted the landlord who got a glazier to come in and fix it. Boulter was on the team who arrived at their home.

Nortessa, who had just returned from travelling, was introduced to Boutler by her mother. Shortly later they began dating and eventually moved in together.

"I realised really quickly how dangerous it was and that, before I knew it, I was kind of stuck, like geographically, stuck in his presence.

"He was incredibly jealous, obsessive and controlling to a degree that I had never experienced before. He wanted to control every part of me as if I was a thing that he owned from what I wore to who I spoke to, to what I said, and if any of those things were out of his control, he got really violent."

The couple only dated for about five months, with Nortessa saying she spent the final two months trying to actively leave him.

She made two complaints to police of domestic violence by Boulter. The first was on September 1, 2010 and the other was on October 12, 2010. After each incident, he was charged with assault.

After the final incident, the police offered Nortessa the option of going to a women's refuge, which she did before moving up north to her family on Great Barrier Island.

On December 15, 2010, Boulter was released on bail at the Invercargill District Court to appear again on March 17 2011. Bail conditions included no contact with Nortessa and residing at a Southland address.

Shortly before Christmas 2010, Boulter decided to travel to Auckland to try and find Nortessa, arriving on December 26 to stay with a friend in Papakura, according to court documents obtained by RNZ.

On New Year's Eve, he sent a Facebook message to Nortessa saying he was going to kill himself. She did not read the message until January 4, when he began messaging her again, writing words that a judge would later say could have been interpreted as a threat to kill her.

Nortessa complained to police about the messages.

On January 17, Boulter booked a one-way trip to Great Barrier Island from Auckland city using a fake name.

The ferry left Great Barrier at 7am on January 20, arriving at Tryphena Wharf about 11.30am. He then travelled more than 8kms to Nortessa's home.

He waited until it was dark to go inside the house. Nortessa was home with another man and her 7-year-old brother and his friend were asleep in an upstairs bedroom.

Boulter hid under Nortessa's bed. When Nortessa and the man went to bed he emerged and struck the man on the back of the head with a hard object, believed to be a piece of wood, knocking him to the floor. He continued hitting him in the head and body.

Nortessa begged him to stop.

"It was terrifying," she recalls.

"It was the worst moment of my life."

Boulter then hit her in the head with the object and continued attacking the man, leaving him unconscious.

Nortessa ran from the room calling for help and Boulter went after her. While they were on the balcony Boulter held her by her leg and hair while dangling her in mid-air. He eventually pulled her back onto the deck.

Moments later he punched her in the back and kneed her in the head making her unconscious.

Boulter then took Nortessa away from the property, holding her hostage in isolated bush for the next 38 hours in inclement weather while she wore only her pyjamas – at times being dragged across undulating terrain.

During the horrific ordeal Boulter attacked Nortessa several times including strangling her.

Nortessa's disappearance had been reported to police with search parties on the island trying to find her.

Nortessa was able to eventually persuade Boulter to throw away his weapon into a stream and led him to the Tryphena Wharf where they came across a search party. The Armed Offenders Squad rescued her, and Boulter was arrested.

"I couldn't think, I was just overwhelmed," Nortessa says of the moment her ordeal came to an end.

"I didn't know what was happening. I didn't know what was going on. I think there was a sense of relief that you've been found, but then going to the state of like realisation once you're out of that survival mode of like what are all these bruises? Why can't I see properly? Why can't I talk properly?"

Boulter would eventually plead guilty to nine charges including kidnapping in relation to the prolonged physical abuse he inflicted on Nortessa.

At sentencing in June 2012, Justice Heath described the offending against Nortessa as "a course of conduct over a protracted period of time during which extreme physical violence was inflicted on Ms Montgomerie".

The judge referred to a psychiatrist report who diagnosed him as having a psychotic disorder.

The psychiatrist said if his symptoms were to persist it could lead to a diagnosis of schizophrenia.

Justice Heath said he had read Boulter's letters to the victims and was unsure about the level of insight he had into his offending and the consequences of it.

"Like [the psychiatrist] I have concerns about your inability to empathise adequately with your victims," he said.

"I am prepared to accept that the underlying mental condition probably removed natural inhibitions that usually prevent human beings from acting in this brutal and callous way. But beyond that, I cannot see any basis for additional credit."

Boulter was jailed for eight years and six months.

Nortessa read her victim impact statement during the hearing.

"He listened to everything he had done to me with a stone-cold look on his face. I was terrified."

She says she was lucky to be surrounded by people at the time who were caring and also honest with her.

"I was told 'this is where the work begins, this is where we start, because the issue is not getting them put in prison for what he's done, it's keeping him in there'.

"It was not sugar-coated to me. I was not wrapped in cotton wool… I didn't have any dreams about him being away forever. I knew how dangerous he was and I had learned what he was capable of and nobody knew how far he would go."

With Boulter behind bars, Nortessa focused on therapy, saying she had to process what had happened to her or it would likely kill her.

"I didn't want to give him that satisfaction. He had so much control over my life, and he stole so much from me that I wasn't gonna make it for nothing… I didn't want him to live inside my body anymore, I didn't want to live in fear."

Boulter made several appearances before the Parole Board before he was eventually released in September 2018.

Nortessa prepared a statement for the board when he first came up for parole.

In it, she wrote that Boulter's actions had "absolutely shattered my sense of wellbeing on every level".

"The terror that I faced during those 38 hours haunts me on a daily basis, where I still find it very difficult to function with normal day-to-day tasks."

She said she was "very slowly picking up the pieces of my life".

"Enough to try and stop looking over my shoulder at every man with the same body shape, or the same tone of voice, and reassure myself that he is still in jail."

She feared if he was let out he would kill her.

"I trust that you will make the safest decision and I beg you not to put my life in this man's hands again because this time I know he will take it."

At his final hearing, the board said he had 13 past convictions including a number for domestic assaults in 2006, 2010 and 2011. He was assessed by a psychologist as being at moderate risk of violent re-offending.

He had recently been approved to work outside the wire and had positive reports.

"Having regard to the strong support available to him in the community and the work Mr Boulter has completed on this sentence, we are satisfied that for the balance of his sentence his risk can be managed by way of parole conditions."

He was released with a series of standard and special conditions for six months.

His conditions included not entering the North Island without the approval of his probation officer and to disclose any details of any intimate relationships.

Less than two years later, on July 1, 2020 Boulter was jailed for two years and five months on a raft of charges including threatening to kill, posting a digital communication with intent to cause harm, and threatening to do grievous bodily harm in relation to offending in Invercargill and Dunedin.

Court documents reveal his victim was a friend of his sister's who he became obsessed with.

Judge B A Farnan referred to messages between Boulter and the woman between September 2019 and February 2020. Initially, the messages were of a "pleasant nature", however they became "aggressive and threatening" from December 11, 2019.

Police carried out a search for the word "leave" in the messages, returning 23 pages of messages. There were 282 messages, of which 266 were sent by the victim, most of which told him to leave her alone.

"It was evident that you had become obsessed with this person to the point that you were stalking her and threatening to kill her."

Several of the messages from Boulter referenced his offending against Nortessa.

In September 2019 the victim stopped replying to Boulter. Boulter sent more than 1300 unanswered communications to the woman between February 3 to February 16.

"The content of the text messages ranged from you apologising to this woman, to subtle and overt threats and abuse of her."

In February 2020, Boulter arrived at the victim's address where his sister was also present.

Boulter's sister met him in the hallway and refused him entry to the house. Boulter became aggressive and started yelling out for anyone in the house to come out and fight him.

He then told his sister that if she did not let him inside he would return with a sawn-off shotgun. He left the property and his sister called the police.

Two hours later he returned and tried using the back door, but it was locked. He left again before police arrived.

He was later arrested near his home.

When she was interviewed by police the victim told them about another incident a month earlier.

Boulter had messaged her implying he was watching her house and that he knew she was home. The victim agreed to meet him outside as her young child was in bed.

Boulter verbally abused her for a number of hours, and told her to kill herself.

The woman told police she was scared and crying.

"She was sitting in a corner when you punched her in the back of the head and kicked her in the lower back."

He then pleaded with her to stay in his life. He eventually left after she said they could still be friends.

In the weeks that followed the incident, Boulter text her five times threatening her. The messages included: "do you know you can't hide from me forever" and "you tell bub anything or anyone for that matter I will gut you like the little pig you are".

In another message on February 13, Boulter said "you shouldn't read my snapchat and texts, you were out all night with a guy, I'm not dumb and when I find out ima murder both of you c**ts".

His Dunedin offending related to when he was in Wakari Hospital due to concerns prison staff had about his mental health.

While in the hospital he threatened to do grievous bodily harm to a staff member.

Boulter's lawyer submitted he was remorseful, that he wanted to move on, and had "limited ability to carry out the threats". She added he was impacted by his mental health and was wanting assistance.

Judge Farnan said it was clear Boulter's mental health had in recent times "significantly deteriorated". While on remand it continued to get worse and he had to be admitted to Wakari Hospital where he spent some time subject of an order under the Mental Health Act.

He said Boulter needed to ensure he took his medication that was prescribed to him on a regular basis.

"Someone in your position with a mental health illness cannot be criticised for having a mental health illness, but you can be criticised if you in fact do not take the medication that is prescribed to you which can keep you well.

"It seems from what [his lawyer] tells me you want to be well and that is positive going forward."

Boulter had an additional nine months added to his sentence in March 2021 after threatening to kill and breaching a protection order.

The charges related to a "fixation" he had on the victim he had offended against in Invercargill who had been granted a protection order.

Judge K J Phillips said Boulter was speaking to a staffer at Otago Correctional Facility about how he had put a cover over the CCTV camera in his cell.

The pair then had a general conversation during which the officer asked him what he intended to do when he was released.

Boulter said he was going to go back to Invercargill and strangle the woman, who he wrongly claimed was his ex-partner. Once he had done that he could get on with his life, he said.

The officer tried to "dissuade" Boulter, who repeated several times that he was going to kill the victim when he was released. The officer reported Boulter's comments.

A few days later, Boulter sent the victim a letter to an address where she previously lived. The letter was of a "conciliatory nature", with Boulter asking to rekindle the relationship and to be given another chance.

The victim only became aware of the letter when the occupant got in touch with her and it was then passed on to police.

Judge Phillips referenced the victim impact statement which said she and Boulter were never in a relationship but she believed Boulter became obsessed with her.

The judge said Boulter had "the most horrendous past history of family violenceе offending at all levels of the criminal code".

Boulter was released by the Parole Board on March 29, 2023 with five weeks remaining on his sentence. The board noted his classification was low.

"The Parole Assessment Report said that Mr Boulter has positive behaviour, and he has said that he is determined not to do this again."

Boulter also told the board he had developed an obsession with the victim, which he attributed to mental health issues and substance abuse. He was taking medication and agreed to continue working with forensics and continue taking his medication.

The Board said Boulter talked about his warning signs being substance abuse and going into an intimate relationship, and how his support people can identify those.

After release, Boulter was in and out of prison. In January 2025 he was released from prison subject to a number of conditions, then on April 14 he was jailed for one month for speaking threateningly.

On May 9, Boulter posted on a tattoo artist's Facebook page asking if they knew any artists in Invercargill or Christchurch that were looking for a "very keen apprentice".

"I'm very passionate about art and creativity but would like to become an award winner in tha tattoo industry! I've had a checkered past but have found a new outlook on life and am no longer just gunna survive it's my time to thrive" (sic).

Three weeks later, he was in trouble again.

On June 1, Boulter approached a young woman working at a shop in Riverton, making unwelcome and unwanted comments about her appearance.

He left, but returned twice, repeating his behaviour.

The shop assistant called her father, who arrived during a subsequent visit by Boulter, and approached him.

Boulter "immediately took offence" and raised his fists and verbally challenged him to a fight.

"The invitation to fight was politely and firmly declined."

Police were called, and Boulter continued to challenge the father at close range until officers arrived and were able to diffuse the situation as Boulter became calm and compliant.

He was removed from the immediate vicinity, however he became "increasingly agitated" and attempted to approach the father again saying he would "smash" him and called him "gutless" for refusing to fight.

Boulter was arrested and declined to comment. He would plead guilty to two charges of behaving in a threatening manner or behaving in a riotous manner that was likely to cause violence. He also admitted a charge from Corrections of moving to a new residential address without prior approval.

"You were reminded by Probation on a number of occasions of the importance of letting them know where you were staying and that you could not move without their approval, showing a disregard for your release conditions," Judge M Williams said at sentencing.

Boulter was sentenced to six weeks' imprisonment, but was released that day. The judge did not impose any release conditions as he was currently subject to conditions until September.

Nortessa says she was "nervous" when she read about Boulter's sentencing.

"All of the experts that I've had to support me over the years have always said that he's not the kind of person that would be working a steady job and be around his family and then all of a sudden hurt somebody, that there would be like a de-escalation.

"There would be a degradation in his behaviours, things would start to fall apart over time, and he would lose the job, and then he would start drinking. There would be a pattern. I saw that as a pattern."

She was afraid of what he might do next.

"My fear for myself is one thing that I can manage but what kept me awake at night is I knew in my heart that his behavior has escalated over the years, and someone, someone's daughter, family member, someone they love was going to be seriously hurt, and I have been trying to stop it, and it feels like we have to wait until someone is in trouble to address it."

Shortly after Boulter's arrest Nortessa learned he was in custody, but not the reason. In the following weeks she discovered he'd been accused of killing a woman.

"It was almost like an out of body experience. I saw what I had been trying to warn people about for years. It made me feel sick. I know what she would've felt - the fear. It's heartbreaking."

She also felt an overwhelming sense of defeat.

"I didn't feel anger. Anger is something you have when you're fighting for something, and I felt like I had just lost the fight."

Then came the questions, how did it get to this? What level of oversight was there?

"So many people were involved in keeping him accountable and medicated. It's the worst-case scenario, this person decides what he wants to take, and no one can protect us."

She thinks back to 15 years ago when she was the target of his "incredibly obsessive" behaviour.

"People who haven't experienced stalking of this magnitude can't understand what it feels like to have someone so singularly focused on having access to you.

"He has such an intention to possess and own a person, I think it dehumanises them to him, and as soon as the person has a voice of their own, or decides that they want to get away from the chaos, I don't think he sees them as a human."

There are several reviews underway in relation to the woman's death.

Corrections director of Communities, partnerships and pathways Glenn Morrison earlier told RNZ Corrections had commissioned a review into Boulter's management, which was standard procedure to identify any areas where we could further strengthen our practices.

"Part of this includes how Corrections has communicated and worked with relevant agencies, including Police."

Canterbury District Commander Superintendent Tony Hill said a Family Harm Death Review was underway.

Nortessa believes the system failed. There needs to be an acknowledgement that the system failed to keep the woman safe.

"The truth is this was avoidable. We can't pretend it wasn't and that it came out of nowhere. He was telling you stuff long before he did this. This is not an isolated incident. This is a consequence of all of the other things building up, it's predictable behaviour."

Looking forward, Nortessa says she would always be prepared to help police keep women safe from Boulter, who she says should never be released from prison.

"I will do whatever I have to to make sure that this doesn't happen again, that he doesn't ever hurt anyone again. I don't care what I need to do or how long it takes, I don't believe that I should have to, but I will, I'll always advocate to keep him in prison.

"That's what the near future looks like for me. It's just like I carry on with my life, but I'm always thinking about how I can make sure that he never hurts something again, me included."

Asked how she would describe Boulter, she takes a long pause.

"I believe that I've seen him as I've always seen him, which is a calculated and dangerous abuser. He's a monster," she says.

"He was telling us who he was all along. It took this for people to listen but I've always known exactly who he was. I see this man as really singular in the way that he stalks women. His focus is obsessive. The way that I viewed him hasn't changed. He's just fulfilled the breadth of what I believed he was capable of."

rnz.co.nz