The killers of toddler Moko Rangitoheriri have each been sentenced to 17 years' imprisonment at the Rotorua High Court today.

Justice Sarah Katz handed down the highest sentence imposed in New Zealand for the manslaughter of a child. It will see David Haerewa, 45, and Tania Shailer, 26, serve a minimum of nine years in prison.

Moko Rangitoheriri's killers were sentence to 17 years' imprisonment at Rotorua High Court today. Photo: Supplied.

In an emotional victim impact statement, Moko's mother Nicola Dally-Paki held back tears as she addressed the killers directly.

Tania Shailer has been sentenced to 17 years for the killing of Moko Rangitoheriri. Photos: George Heard/Fairfax NZ.

"Tania you were meant to be my friend. Someone that I could trust and instead you tortured and killed my baby," she said.

David Haerewa was also sentenced for 17 years for killing Moko Rangitoheriri.

"David, I did not know you well, but I now know both you and Tania as monsters. You subjected my children to hell. I believe you subjected your own children to hell as well. I feel for your children, my heart breaks for them as well."

The pair were initially charged with murder before pleading guilty to the lesser charge of manslaughter.

Haerewa showed little emotion the entire time he sat in the dock looking at his feet only once looking up to look at the judge.

Meanwhile Shailer, also looking down, could be seen shaking her leg with a scared look on her face, now and then she would look up and make eye contact with Nicola.

With a family member at her side, Nicola described the trauma her son's brutal death has had on her remaining children, and that she was now battling with Child, Youth and Family to have them returned to her care.

"The pain and upheaval in my children's and my life is never ending. I have to fight to get Moko's brother and sister back into my care because of Tania and David's actions.”

Nicola told the court she wished she could take the place of her son and the terrible beating he took from both Haerewa and Shailer.

'I would take the beatings, the horrific abuse that they gave my son. I would take being kicked and bit, I would take all of the torture if that would save Moko's life."

Nicola then asked the court not to show any mercy to the pair as they had shown none to her son and the beatings he had to endure for six weeks.

Moko's grandmother Nicky Rangitoheriri also addressed the court saying the trauma of seeing her grandson through the 'window of the mortuary” had brought her nightmares she would lose another grandchild to abuse.

"The offenders choose to torture him every day, choose to take his life. . . they don't deserve forgiveness your honour, they deserve to be locked away for life for murder."

Moko's uncle Anthony also addressed the court saying finding out how his nephew died made him 'physically sick”.

'The deepening anger on hearing the truth, the depth of evil, right up to his last breath. It bought me to my knees. You two, without an ounce of regret, tortured Moko to death."

‘A CULTURE OF VIOLENCE AGAINST MOKO EVOLVED'

Crown lawyer Amanda Gordon told the court the level of violence inflicted on Moko was incredible and the 'culture of violence had reached the level of torture”.

Ron Mansfield, defence lawyer for Shailer, argued his client was under mental stress after herself being a victim of domestic violence was taking prescribed medication and was using alcohol and cannabis at the time of the abuse.

"Her actions are entirely attributable to her mental illness, not because she is evil."

He also claimed Nicola was aware of Shailer's use of cannabis because Nicola had supplied her with it in the past.

Haerewa's lawyer Harry Edward says his client is a secondary participant in the offending and it was Shailer's stomping on Moko's stomach that had been a contributing factor in his death.

Edward says his client, a diagnosed schizophrenic who is on medication, was not told the two children were coming to stay and they were already financially struggling with their own four children.

He also says Haerewa also co-operated with the police in submitting to a dental check.

"[Proving] he could not be the person responsible for the bite marks on Moko's left cheek and right shoulder."

"In summary, David Haerewa was completely out of his depth. He was unaware of if and when the children would be returned to their mother," says Harry.

Summing up, Justice Katz described the appalling catalogue of abuse suffered by Moko.

"The degree and severity of the assaults escalated, a culture of violence against Moko evolved. Miss Shailer was observed by children in the house to punch, slap and kick Moko," she says.

'Mr Haerewa, you admitted to police you assaulted Moko repeatedly.

"Throwing him with force onto his bed, the stomping on his back.

Katz also said the couple lied to police, saying his injuries were self-inflicted and dismissed defence claims of greater culpability.

"Any differences in culpability between you are relatively minor. You both assaulted Moko continuously, yours was a joint enterprise," she says.

"The extremity of the violence, multiple acts of violence, the breach of trust involved in your offending are all at the most serious end of manslaughter."

Katz says only one other manslaughter case in New Zealand featured worse abuse.

While skeptical of some of the mental health claims made on Shailers behalf, Katz says she is entitled to some discount, though she declined to offer any discount for remorse.

Both were entitled to discounts for early guilty pleas however, especially as it saved children from giving evidence.

MOKO'S SHOCKING ABUSE

The summary of facts for the case paints a grisly picture of Moko's last days. During the two months he was with Haerewa and Shailer, he was kicked, thrown, dropped face first on the floor, bitten, stomped on, had faeces rubbed on his face and was denied medical care.

The abuse only came to light after his little body could take no more punishment. On August 10, 2015, Shailer called for an ambulance after Moko became unresponsive.

She said Moko was very cold, not breathing and his stomach was hard. She said Moko had fallen from a woodpile.

Paramedics arrived to find Moko lying face down in the home's hallway. Shailer was by his feet while Haerewa kept the other children away from the paramedics.

Ambulance officers realised Moko's condition was dire. All they could do was scoop him up and rush him to Taupo Hospital.

He arrived with swelling to his face so bad it was impossible to open his eyes. His abdomen was distended.

He had bruising on his front and back. Multiple abrasions and wounds that appeared to be human bite marks were found on his face and arms.

Starship Hospital was called at 3.45pm and plans were made to move Moko north to the hospital where his mother and sibling already were.

But he could not be revived and was pronounced dead at 10pm. Shailer asked hospital staff if Moko would have survived had medical attention had been sought earlier, the summary of facts says.

A homicide investigation began and a post-mortem was undertaken.

It was difficult to determine the exact cause of death due to the number of injuries. Lacerations and a haemorrhage deep within Moko's abdomen, coupled with a bowel rupture - likely caused by being stomped on by Shailer - was one potential cause. The other cause of death could have been swelling to the brain from repeated blows to the head.

His injuries included facial and neck contusions and abrasions; human bite marks on the left cheek, right cheek and arms; lacerations to his chin, neck, ears and lip; haemorrhages to both eyes; and multiple abrasions and contusions over the skin of his chest and abdomen. His bowel was also ruptured, causing infections, making him very weak.

Both defendants supported each other's attacks on Moko and the "culture of violence" that occurred within the home, the summary of facts says. The viciousness increased over time.

Shailer was observed by a witness biting Moko and Haerewa admitted to continually attacking Moko. He said it became routine to pick on Moko and he didn't want him around him.

Two of the child witnesses said it was Shailer who stomped "really, really hard" on Moko's abdomen and stomach. It was after this act, thought to have occurred on Thursday, August 6, 2015, that Moko's body starting rapidly giving up.

On that Thursday, Moko was soiling himself uncontrollably. By the Sunday, Moko could barely walk. He started falling to the ground, was vomiting often and was unable to stop defecating.

Both Shailer and Haewera were at home the entire day with Moko, but no medical treatment was sought. Haewera kicked Moko in the back after he defecated on this day. Shailer held his mouth shut to silence him.

On Monday, August 10, Moko was unable to speak and could barely move. His stomach became hard. Breathing was laboured. Shailer walked her children to school and at midday went to attend a course.

On her trip home about 2.20pm, she told a friend Moko had fallen from a woodpile. Her friend was concerned and said it was best to have him checked out in case he had a head injury. She even offered to drive them to the hospital. Shailer declined.

Forty minutes later, she would make the 111 call that brought their violence to light, but it was too late to save Moko.

Shailer at first said Moko's injuries were a result of Moko doing things to hurt himself, the summary of facts says. She said Moko had fallen from the bunk bed. She said he would rub his neck against the table and even run into the walls head first.

She also said Moko had pleaded with her not to take him to hospital after he had "fallen off the woodpile".

At that time, Moko was unable to walk, let alone say anything.

Additional reporting: Stuff.