The trial for a woman accused of murdering her partner at his Ashburton home has started - more than four years after the violent killing.

Peter Tawhiwhiorangi Hemi, 23, was stabbed to death at his McDonald St home on November 8, 2019.

Days later his partner, Kia-ara Richardson, then 19, was charged with murder.

She denies the charge and is on trial in the High Court at Christchurch before Justice Cameron Mander and a jury.

Peter Hemi. Photo / Supplied

Full details of Hemi’s death - just two weeks after the birth of the youngest of his three children - were shared for the first time in court today.

Crown prosecutor Andrew McRae told the jury that the alleged murder followed a fight between Richardson and Hemi regarding their plans for the night.

The couple had been to a party in Tinwald but returned home after Hemi had an “altercation” with another woman.

During the fracas, Richardson was seen to “pull out a knife”.

McRae said that showed Richardson was in possession of a knife the night Hemi died.

“It wasn’t unusual to see the defendant in possession of a knife … in fact, both (Richardson and Hemi) were often seen in possession of knives,” he said.

The jury would hear that knives were seen around the couple’s home and in their vehicle by multiple people.

After the incident, the couple returned to McDonald St, where they have lived for a week.

Hemi wanted to go to another party but Richardson wanted to stay at home which sparked the fatal fight.

The couple were heard arguing and McRae said there was abuse hurled “both ways”.

It was a very heated argument - so much so that a neighbour began to film the pair.

Hemi got into a vehicle and Richardson climbed into the back seat.

The arguing continued and Hemi was heard shouting at Richardson to “f**k off” and “get out of my face, bitch”.

And then there was silence.

“The Crown say at this point, in a moment of extreme anger borne out of the hurtful verbal tirade, she stabbed Mr Hemi in back of the head,” McRae said.

“It penetrated his skull … the estimated depth of the wound was 13-15cm.

“(Richardson) pulled that knife out two or three seconds later. She got out of the car, slammed the door shut, walked to the fence line of the property and disposed of the knife by throwing it in the long grass.”

She then went back to the car and opened the driver’s door, McRae explained.

Hemi fell out on to the ground.

“He was bleeding significantly and was clearly dying … He called weakly for help,” said McRae.

Hemi was heard screaming “I’m bleeding out, f**king call an ambulance, I need help.”

Richardson started to scream for help but then called 111 herself.

Kia-ara Richardson on the first day of her trial for the alleged murder of Peter Hemi. Photo / George Heard

McRae said the jury would be played that call later in the trial.

He said what Richardson said to the 111 calltaker was “very significant”.

He would not be elaborating on what she said until after the jury had heard the call as it was crucial they listened to Richardson’s voice “free from any influence”.

McRae said Richardson claimed Hemi stabbed himself in the head.

That when they were in the car he turned and “looked at me as if he hated me”.

She got out of the back seat and walked to the driver’s door and by the time she opened it Hemi had stabbed himself, she claimed.

McRae said the knife used to kill Hemi was not found at the scene and has not been located since.

“That is the principal issue for the jury - who it was that inflicted the wound,” he said. “Was it the defendant or did Mr Hemi do it to himself? There was no knife near Mr Hemi or in the surrounding area when he died. You might ask yourself if Mr Hemi had done that to himself - how may that be?”

He told the jury the answer was simple.

“The defendant, in anger, stabbed her then-partner with a knife in the back of his head, causing his death soon after,” he posed.

The Crown said it was clear Richardson intentionally stabbed Hemi, or, at the very least, she intended to inflict an injury that could cause death and was reckless as to whether death ensued or not.

McRae said the jury would hear more about Hemi from witnesses about his life, his association with the Nomads gang and his relationship with Richardson.

Some of that background would “not endear” Hemi to the jury but McRae urged them to listen to all of the evidence dispassionately and without judgment.

He said despite the way he “treated” and spoke to his partner, there were also times when their relationship was “good”.

“Miss Richardson was clearly devoted to him - and that’s why the things that were being said that night were so hurtful to her and made her do what she did,” he said.

The court also heard that on the day Richardson was arrested, she had a large fishing or hunting knife in her possession. It could not be linked to the alleged murder.

During the trial the jury will hear from more than 50 witnesses including Hemi’s mother, Te Atatu, and his brother, Aaron, and people who witnessed the couple’s altercation that night and the alleged murder.

Kia-ara Richardson's trial is expected to run for three weeks. Photo / George Heard

The jury would also be shown video footage of the alleged murder taken by a neighbour.

A number of police would also give evidence about the scene examination and homicide investigation.

“This case is all about who stabbed Mr Hemi - did he do it to himself, or was the defendant responsible?” McRae said. “The defendant was responsible for this injury to Mr Hemi … She was angry at him and she took the anger out on him.”

McRae said the evidence would clearly support the Crown case.

Richardson’s lawyer, Rupert Glover, briefly addressed the jury before the first witness was called.

He said while McRae’s opening was “pristine and contradictory at this stage” it was crucial they listened to all of the evidence.

“Don’t be fooled by my friend’s confidence,” Glover said. “Keep your eyes, ears and, above all, minds open.”

The trial is expected to run for three weeks.

Anna Leask is a Christchurch-based reporter who covers national crime and justice. She joined the Herald in 2008 and has worked as a journalist for 18 years. She writes, hosts and produces the award-winning podcast A Moment In Crime, released monthly on nzherald.co.nz