A young mother has been found guilty of murdering her 21-year-old partner Brendon Hamilton.

Almost two years after Hamilton died in his Dominion Rd flat and more than two weeks after Rikki-Lee Simeon pleaded not guilty to murder, jurors reached a verdict at 3.40pm on Thursday.

Hamilton, 21, was stabbed in the neck in the Mt Eden apartment and died the same day he and Simeon's daughter Shyanne turned 1 year old.

Brendon Izaac Lee Hamilton was 21. Photo / Supplied

The unanimous guilty verdict at Auckland High Court brought some tears of relief to Hamilton's family, who'd waited for justice since May 18, 2019.

But everyone in the public gallery, including Simeon's supporters, was largely composed and quiet in the moments after the verdict was announced.

Hamilton's loved ones outside the courthouse described their relief, one saying a burden was lifted from his shoulders after nearly two years.

Crown prosecutors Kirsten Lummis and Steven O'Connor presented a case suggesting Simeon had a history of being a violent, abusive girlfriend.

And the prosecution said even if Simeon felt threatened, her use of a 30cm kitchen knife against Hamilton in the early hours of May 18 was unreasonable.

The Crown also said Simeon after her arrest provided meandering, unbelievable accounts of what happened in the apartment.

Simeon was 18 at the time. Baby Shyanne lived with Hamilton's mother Adoniah Lorigan in Rotorua.

Simeon old a crime scene sergeant she stabbed Hamilton, then backtracked, then told a detective she had stabbed Hamilton, but by accident.

The defence said jurors could not rule out self-defence, and said police interviewed Simeon in questionable conditions, when she was hungry and deprived of sleep.

Defence counsel Paul Borich QC and John Munro advanced a case urging jurors not to be sidetracked into speculation about what might have happened in the flat.

The defence said the relationship was not one of a vicious girlfriend and browbeaten boyfriend, but that Hamilton was capable of violence and aggression.

Borich said the Crown presented a slew of superfluous information which took jurors no closer to knowing how or why the stabbing happened.

"We cannot of course look into Miss Simeon's mind," Justice Neil Campbell said as he summed up the case on Wednesday morning.

Justice Campbell said the Crown had to persuade jurors Simeon used unreasonable force in the circumstances.

The prosecutors said Simeon consciously ran the risk Hamilton would die as a result of her using the kitchen knife and stabbing him in the throat.

Two security guards flanked Simeon in the dock as she was convicted of murder.

She at one point briefly tilted her head back, then nodded when Justice Neil Campbell advised the court Simeon was to be remanded in custody.

Simeon will be sentenced on April 13.