His family came to support Jason Heihei during his appearance this week and some were visibly in tears as the guilty plea was entered.
A bearded Heihei broke down when the charge was put to him and it took him a few seconds to plead.
Justice Anne Hinton convicted him and ordered a pre-sentence report. She remanded him in custody to reappear for sentencing on October 24.
He was given a three strikes warning, meaning if he is convicted of a qualifying offence in future he will serve the full sentence, without parole, unless the court considered that would be manifestly unjust.
Ms Ellis asked if the sentencing could be brought earlier to bring closure to Heihei's family who may want to address the court at his next appearance.
The court, she said, may also request a report on restorative justice as the families of Corey and Jason Heihei were in regular communication.
Heihei first appeared in the Kaitaia District Court on July 23 last year charged with murder and was given interim name suppression.
At an earlier appearance in the High Court in August last year, the case was adjourned to give him more time to talk to Ms Ellis before a plea could be entered.
The court indicated Heihei would be entitled to full credit if he entered a plea at his next appearance which he did on Thursday.