WARNING: This story includes details of child abuse and may be distressing for some readers.

The murder of five-year-old Malachi Subecz in Tauranga happened at the hands of a caregiver his uncle has called a monster.

Malachi Subecz died in November last year while in the care of Michaela Barriball, who was sentenced to life in prison with a non-parole period of 17 years on Thursday.

Malachi was beaten, starved, burnt and thrown against walls.

Barriball had pleaded guilty to murder, plus charges of ill treatment of a child and injuring with intent to injure.

The boy's uncle, Peter Menzies, gave an victim impact statement in court, saying the little boy was in the care of monsters.

Peter said he can longer get a full night's sleep without seeing his nephew gasping for breath in hospital.

"Malachi died in my arms 42 hours after life support was turned off. From that moment, my confidence and happiness died too.

"I do not regard you as a human being," he said, addressing Barriball. "What you did is not even primeval. Those who knew and did nothing are just as bad and should be similarly punished."

Malachi's mother, Jasmine Cotter, said her son's birth saved her life.

Michaela and Sharron Barriball in the High Court at Rotorua facing their sentencing. Photo: RNZ / Leah Tebbutt.

She said she no longer knew how to move through life without him.

"I don't know anything anymore, I cannot express the significance of his loss.

"Seeing him in the hospital was one of the scariest I have ever had to endure."

Justice Davison detailed how Malachi faced months of abuse on a daily basis.

It started in June 2021 when Malachi was placed into the care of Barriball.

The summary of facts stated Malachi was slapped on the head, face and body. He was also held under water and pushed by his chest into a wall.

As a result of the abuse, the boy would soil himself. Barriball punished him by stripping his clothes off and locking him outside.

Malachi was acutely malnourished at the time of his death weighing 16 kilograms - lighter than his weight as a 3-year-old, Justice Davison said.

Malachi also was severely burnt by hot water, leaving blackening wounds on his abdomen.

Justice Davison said the abuse Malachi faced was at the highest end of any scale and was nothing less than torture.

"You held all the power and you abused that power in the most callous and inhumane way imaginable. Your abuse clearly sits at the highest end on any scale."

He told Barriball that Malachi was clearly a loving boy who must have been bewildered by her brutality.

"This was a murderous attack by which you intended to kill him.

"This was another cold-hearted attack on this defenseless child, subjecting him to a violent and brutal beating inflicting what were fatal injuries."

Barriball's sister Sharron Barriball was also sentenced to six months' home detention for perverting the course of justice.

Outside the courthouse, Malachi's aunty Helen Menzies delivered a statement from the family.

"As a family, we are still devastated by the loss of our much-loved Malachi's life," she said.

She said the family was aware of an ongoing investigation with Oranga Tamariki's handling of the case.

"It is our hope that the significant failings become apparent in this investigation and that all failings in the system are fully addressed with legislative changes to follow.

"When this happens, we will know that Malachi's voice has been heard."

At the time of the murder, Children's Minister Kelvin Davis said he would "get to the bottom" of what involvement Oranga Tamariki had with the boy and his care.

In a statement on Thursday, Davis said Oranga Tamariki's chief social worker was working on a thorough review into the death.

"I have made it clear that this should be thorough and that if the response at the time was not good enough, regardless of the agency involved, then changes will be made," he said.

"It is too soon to jump to any conclusions about what could have been done better or areas that need to be looked at, but once the investigation is complete I will be able to comment further."

-RNZ.