Michael Curtis and his brother Wiremu. Photo / Alan Gibson
The two brothers who killed Nia Glassie later turned on each other in prison, one ordering a "hit" on the other because he thought he was a "nark".
Their mother learned of the threat and called police, begging them to protect her younger son from the older.
Michael and Wiremu Curtis were last week found guilty of murder in the High Court at Rotorua, the jury accepting the Crown case that the brothers fatally kicked the 3-year-old in the head.
Nia's mother, Lisa Kuka, was found guilty of manslaughter, and two others, Michael Pearson, 20, and Oriwa Kemp, 18, were found not guilty of manslaughter.
William Curtis, the father of Michael, 22, and Wiremu, 18, has pleaded not guilty to grievous bodily harm and will stand trial separately.
However, the Herald on Sunday can reveal that Michael Curtis - affiliated to Black Power - ordered a "hit" on Wiremu shortly after the six accused were arrested for the death of Nia in August last year.
Wiremu, just 17 at the time, wrote to his mother Tania Te Para-Heta claiming his older brother believed he was the "nark".
Michael Curtis is also believed to have called his mother that same day, asking where his brother was in Waikeria Prison.
Fearing for her youngest son's safety, Te Para-Heta rang Rotorua police, claiming Michael had "put out a hit" on Wiremu.
She faxed the letter from Wiremu to police, who forwarded it to the Department of Corrections.
Detective Constable Mark van Kempen, a leading officer in Operation Pedigree investigating Nia's death, sent an email to a Corrections officer warning of the threat.
He wrote on August 23 last year: "The last time that Michael and Wiremu came into contact with each other was in Rotorua at the court. Michael refused to speak to Wiremu as he claims Wiremu is the nark.
"Michael and William are very tight as father and son and Wiremu is definitely on the outer."
During the four-week trial, the Curtis brothers were separated in the dock by a prison guard after Wiremu Curtis made a cut-throat gesture to his brother and a scuffle broke out in court.
Nia Glassie died in Starship hospital in Auckland on August 3 last year after sustaining massive injuries to her head.
Her mother, Lisa Kuka, did not take her to hospital for nearly 36 hours, crucial time which may have cost the child her life.
At first, Michael and Wiremu Curtis told Lisa Kuka that Nia was hurt when she fell off Wiremu's shoulders while Kuka was working, on Friday July 20.
However, in subsequent interviews with police, the brothers admitted they had abused Nia by performing wrestling moves on her, putting her in a tumble dryer and spinning her off a clothesline.
Wiremu and Michael admitted being involved, but blamed the other for being more abusive.
The pair denied kicking the toddler in the head, believed to be when the fatal injuries were inflicted, but were found guilty of murder.
A Corrections spokeswoman declined to comment on the security arrangements, location or circumstances of individual prisoners to ensure the security of prisons is maintained.