A Samoan father-of-five was sentenced to 24 years in jail by the Supreme Court of Victoria for brutally stabbing and killing his wife in 2023, over a baseless suspicion that his wife was having an affair with his brother.

Rimoni Muliaga, 44, repeatedly thrust a large kitchen knife into Lise Muliaga, 37, in the garden of his brother's bungalow in Melton South, on the outskirts of Melbourne, on 18 September 2023, just weeks after the family had moved from New Zealand.

Three of their young children, aged 12, seven and five, witnessed the horrific assault.

On Wednesday, the Supreme Court of Victoria Justice James Gorton condemned Muliaga for the murder

The judge described the killing as 'an act of the most serious domestic violence against an innocent and unarmed woman' that 'warrants serious condemnation'.

The court heard that Muliaga attacked his wife with a knife, stabbing her four times - twice in the right shoulder, once in the left upper chest and once in the left breast.

The fatal injury was a 9.5cm stab to the upper chest that sliced through two ribs, severed two major blood vessels, resulted in substantial blood loss, punctured the chest cavity and damaged a lung.

Mrs Muliaga had fought for her life, sustaining defensive knife wounds to her arms as she desperately attempted to fend him off.

"It was a frightening and violent death," stated Justice Gorton.

When family members rushed to the backyard, they discovered Mrs Muliaga seated on the ground, the knife still lodged in her shoulder, bleeding heavily.

Muliaga was observed standing over her. His sister-in-law shouted at him, questioning his actions.

The murderer fled up the street but later claimed: 'Lise and (his brother) were sleeping together.'

Muliaga's brother dialled triple zero and performed CPR, but despite briefly reviving a heartbeat, Mrs Muliaga was pronounced dead at 2.33pm.

Muliaga was apprehended nearby, his hands still stained with blood.

The court was informed that he repeatedly requested his 'mental health medication' from police and stated he hadn't taken it since the previous day. Justice Gorton observed that Muliaga appeared genuinely shocked and upset upon learning of his wife's death, even asking to phone her. A jury found Muliaga guilty of murder in December following a trial during which he confessed to the stabbing but disputed his intentions.

The court heard that Muliaga was born in Samoa in 1981, one of nine siblings, and had a troubled childhood involving physical abuse.

The court was informed that Muliaga had a low IQ of just 61, placing him in the bottom 0.5 per cent of the population and meeting the criteria for intellectual disability, along with impaired executive functioning and rigid thinking.

He had a history of mental health problems, including depression with psychotic features and a previous diagnosis of schizophrenia in New Zealand.

A forensic psychiatrist who evaluated Muliaga concluded he suffered from a major depressive disorder rather than schizophrenia.

Whilst the court acknowledged that the condition lessened his moral culpability, Justice Gorton emphasised it did not excuse the crime.

Muliaga, who is not an Australian citizen, is anticipated to face deportation upon release.