Two shop workers were stabbed to death as they ate lunch in the back room of a Takanini pawn shop.
They did nothing to bring it on themselves, a jury in the High Court in Auckland was told.
"They didn't see it coming. The whole thing took three minutes," prosecutor Karen Chang told the High Court today.
Zarn Tarapata, 25, is charged with murdering pawn shop owner, Paul Fanning, 69, and an employee, Paul Matthews, 47, at Ezy Cash loan store on Great South Rd, Takanini, on July 19 last year.
He has admitted killing them but pleaded not guilty on the basis that he was legally insane at the time.
The Crown contends that although driven by jealousy and paranoia and though Tarapata was clearly not thinking straight, the defendant knew what he was doing and that it was morally wrong and must therefore be held responsible.
Tarapata has told psychiatrists he had killed the men because "God had told him to do it", said Ms Chang in her opening address.
But the Crown said Tarapata was driven at least in part by jealousy sparked by delusions that his partner, who worked at Ezy Cash, was having affairs with several men including the two victims and that he was not suffering from a disease of the mind and knew what he was doing was wrong.
Ms Chang said this could be seen in his actions at the time of the killings and after as he hid and tried to destroy evidence.
She said he was a longtime cannabis user and had recently been taking methamphetamine. He also had a fascination with combat and weapons, and had a collection of knives.
Defence lawyer Bruce Hesketh told the jury that while Tarapata killed the two men, the question was why, "and that is where the Crown and the defence part company".
The defence, which will call two psychiatrists, say Tarapata suffers from a disease of the mind and had suffered a psychotic episode. This and his reading of the Bible had led him to think he had been commanded to destroy the two victims.
The trial before Justice Pamela Andrews and a jury of six men and six women is set for three weeks.