A High Court jury found double convicted murderer Graeme Burton guilty of trying to kill fellow inmate Dwayne Marsh.
The jury retired on Wednesday morning and returned five times to ask questions and review CCTV footage of the attack, before returning with the guilty verdict on Thursday afternoon.
The footage showed Burton entering Marsh's cell and chasing the inmate around their Auckland Prison cell block, brandishing a weapon in each hand, in December last year.
The Crown argued that Burton used a 31cm stainless steel rod to stab Marsh at least seven times, while he and other inmates were allowed time outside their cells in the prison's maximum security wing.
The defence conceded the attack did take place, but said the Crown had failed to prove Burton intended to kill Marsh.
Burton, 38, is already serving a life sentence, with a non-parole period of 26 years, for the murder of Karl Kuchenbecker in 2007 while on parole, having served 14 years of a life sentence for the murder of Paul Anderson in 1992.
Burton, who has a prosthetic leg, was flanked by up to six security guards throughout the course of the trial.
He will be sentenced at the High Court on 15 December.
Premeditated - police
The officer in charge of the investigation, Detective Shane Page, says he is pleased Burton has been found guilty of what he describes as a premeditated incident.
"I think he's in a situation where he has got nothing to lose, as far as what goes on in prison. I think he's intelligent; and I definitely think he's calculated in what he does. I think there is always a motive behind what what he does."
He says police brought the case to court to show Burton that he is not above the law, even whilst he is in prison.
Mr Page says the investigation was difficult due to Burton's uncooperative nature.
He says he has spoken with Marsh's sister, who has expressed her satisfaction with the verdict.
Burton's lawyer, Peter Tomlinson, told Checkpoint the jury obviously struggled with the case, as it took two days to reach a verdict.
Mr Tomlinson said Burton was easy to act for, was clear in his instructions and was easy to talk to.
