A spurned lover and stalker with a disturbing, violent past pounced on a Christchurch mum and stabbed her 55 times in front of her children.

Details of Nathan Boulter’s brutal slaying in July this year can now be revealed after he entered a shock guilty plea to the woman’s murder at the High Court in Christchurch this morning.

The summary of facts, released by the Crown, outlined how 36-year-old Boulter and the woman – who has been granted name suppression – had entered into a brief relationship in May.

However, once Boulter was recalled to prison, the victim terminated the relationship and told him she did not want any further contact from him.

Boulter soon developed “an unhealthy fixation” with the woman and once he was released, started a “significant electronic harassment” of her.

Between July 7 and July 20, Boulter made 581 calls to the woman – which she tried to ignore.

He used multiple cell phone numbers and social media profiles to harass, stalk, and threaten the victim, the Crown says.

On July 14, he emailed her: “Ima chop u down to nothing hoe put u on the level narcissistist hoe”. And then: “One two guess who’s coming for you! Your lack of human compassion and empathy will be the death of you one day soon my Lil hoe! Xxx.”

Due to her concern and fear, the victim began locking her front gate with a padlock to keep herself safe.

She told her friends and family about the threats.

The day before his murderous attack, he bought a 19cm pig sticker knife from a city hunting store.

Then, at about 6.50pm on July 23, he lay in wait outside the woman’s house on Lamorna Rd, Parklands, that she shared with her two children, her flatmate, and her flatmate’s two preschoolers.

Nathan Boulter appearing at the Auckland District Court in 2011. Photo / David Rowland

He concealed himself behind a tree opposite the house and when she came home with her kids at about 7.51pm, he crept up behind her and attacked in the driveway.

He started stabbing the victim in a frenzied attack, leaving behind a total of 55 stab wounds, the Crown summary of facts says.

“The victim’s children ran into the house as the defendant was stabbing their mother.”

The wounds were significant and included multiple trauma wounds to the head and face, causing extensive damage.

There were self-defence wounds around her hands and arms as she tried to protect herself.

There were further wounds all over her back and torso as well as through her knees.

Her injuries were so significant that she died within minutes.

Boulter left the scene and entered a stranger’s house on Queenspark Dr and put the knife he used to stab the victim on their kitchen bench.

After briefly conversing with the occupants and being told to leave, the defendant went outside onto the driveway of the address, the summary says.

He then phoned his stepfather and then to police via 111, saying on both calls that he had “just killed his ex”.

He told police: “I just killed her now, I stabbed her to death, I f***** up, bro, I need you guys to come get me, I just killed her bro.”

He was arrested by police a short distance from the Queenspark Rd address.

Boulter will reappear next month for a sentencing date to be set.

A violent past

Boulter, 36, has a horrifying history of violence against women, including a high-profile kidnapping on Great Barrier Island in 2011.

In January 2011, Boulter subjected his ex-partner Nortessa Montgomerie, then 21, to physical attacks and terrifying threats over 38 hours after he bashed her unconscious and dragged her from her father’s home on Great Barrier Island.

Montgomerie’s ordeal only ended when she managed to convince Boulter that she wanted to leave the island with him. Police said in doing that, she saved her own life.

Boulter pleaded guilty to nine charges, including kidnapping and wounding with intent and was sentenced to eight years in prison.

Nathan Boulter hid under a bed before attacking his former girlfriend and her boyfriend. He then dragged her through rough terrain on Great Barrier Island, threatening to kill her and himself. Photo / Richard Robinson

The court heard that, in 2010, Boulter and Montgomerie were in a relationship and living together in Southland.

He was charged with assaulting her after two separate incidents in September and October. Boulter was released on bail and was ordered not to have any contact with his victim – and to remain at his approved address in Southland.

To avoid any further contact with her abuser, Montgomerie moved back to Auckland, to her father’s home on Great Barrier Island.

On Boxing Day, Boulter breached his bail conditions and travelled to Auckland to try and find Montgomerie. On New Year’s Eve he sent her a message saying he was going to take his own life. Four days later he sent a second message threatening to kill her.

On January 17, Boulter booked a one-way ferry ticket to Great Barrier Island under a false name. He arrived at 11.30am and made his way to Montgomerie’s father’s home.

He waited until it was dark and then entered the house and hid under Montgomerie’s bed.

She was at the house with a male friend, her 7-year-old brother and his friend.

When Montgomerie and the other man went to bed, Boulter struck. He hit the man on the back of the head with a hard object, continuing the assault when the man fell to the floor.

Montgomerie begged Boulter to stop and in response, he hit her in the head. He hit the man repeatedly until he was unconscious and then chased after Montgomerie, who had run for help.

He caught the 21-year-old and dangled her over a balcony by her leg and hair. He dragged her back up and rendered her unconscious by punching her in the back with your fist and kneeing her in the head.

Armed with “a weapon resembling a thistle grubber” Boulter took Montgomerie from the house.

Dragged, abused, threatened

For 15 hours and during a fierce storm, he held Montgomerie – wearing only a singlet and pyjama bottoms – in isolated bush.

“At times you dragged her across undulating terrain in the bush … you abused her physically over this period. That abuse included physical attacks and strangulation that led to serious injuries. Your intent in doing so was to cause really serious harm to her,” said Justice Paul Heath Boulter’s sentencing.

“After all of that, Ms Montgomerie was able to persuade you to dispose of a weapon by throwing it into a stream and to walk together towards the wharf to escape. Later in the day, searchers located the two of you. Ms Montgomerie’s ordeal finally came to an end.”

Justice Heath said Boulter’s offending “involved a pre-conceived plan to travel almost the full length of this country to confront” his victim.

Another woman attacked

In 2020, Boulter was back before the courts after offending against a second woman.

The woman was a friend of Boulter’s sister in Southland who he started messaging and soon became obsessed with.

He became aggressive and threatening, he stalked her, and he threatened to kill her.

On one occasion, he went ot her home and later threatened his sister that he would return with a sawn-off

On another occasion, he assaulted the woman and “advised her to kill herself”.

Boulter was sentenced to three years and two months on seven charges of threatening to kill, contravening a protection order, assault with intent to injure and causing harm by digital communication.

He was refused parole a number of times – including when the board learned he had not undertaken any rehabilitation programmes in relation to his offending.

But by April 2023, Boulter managed to convince the board that he could be released safety back into the community.

Parole Board panel convenor Mary More noted Boulter’s “serious” conviction history.

Alongside the Montgomerie kidnapping and stalking, there were a raft of convictions for “other violence, kidnapping and burglary”.

For six months, Boulter was ordered to live at an approved address, not to consume alcohol or illicit drugs, not to contact any victims of his offending and to disclose all details about any intimate relationship which commences, resumes, or terminates to his probation officer.

He was not subject to any parole conditions when he murdered the woman in Parklands.

Al Williams is an Open Justice reporter for the New Zealand Herald, based in Christchurch. He has worked in daily and community titles in New Zealand and overseas for the last 16 years. Most recently he was editor of the Hauraki-Coromandel Post, based in Whangamatā. He was previously deputy editor of the Cook Islands News.