The jury in the Arun Kumar trial, in which two boys are facing murder and manslaughter charges, has retired for the night.
A 14-year-old boy is charged with the murder of Mr Kumar at his Railside Dairy in Henderson on June 10 last year. His 13-year-old co-accused is charged with manslaughter.
The pair - who have name suppression - also faced counts of assault with intent to rob, but the Crown withdrew those charges last week at the High Court in Auckland to focus on the more serious counts.
The jury began their deliberations this afternoon and will continue tomorrow morning in search of unanimous verdicts. Justice Lang said it would only be much later that he would consider accepting majority verdicts.
During his summing up this morning, he told jurors if they rejected the 14-year-old's explanation of self-defence, they must find him guilty of murder or manslaughter.
Justice Lang took the jury through a "question trial" designed to help jurors systematically and logically reach their verdicts.
The judge said that, in relation to the older boy, the jury would first have to consider what was in the 14-year-old's head at the time of the attempted robbery. They may also have to decide whether he used reasonable force in the circumstances.
Justice Lang said the Crown's case was clear: the murder-accused used a deadly weapon to a vulnerable part of Mr Kumar's body in a bid to make his escape.
But during their closing addresses last week, defence lawyers asked jurors to look back in time to the factors that had shaped their clients.
Maria Pecotic told the court the 14-year-old had suffered a severe head injury when he was hit by a car six years ago, but was never given the after-care he required.
Neuropsychologist Valerie McGinn gave evidence that the boy had a reduced window of opportunity to think things through when they became complex and would have been acting on impulse when inflicting the fatal wound.
Justice Lang said the matter of "intent" was for the jury to decide if they rejected the notion of self-defence.
Earlier, he told the jury feelings of sympathy and prejudice would arise "on many levels", but that they must be avoided to focus on the facts.
"The most obvious [example] of course is that Mr Kumar was killed and Mrs Kumar left a widow. That was a tragic event and all of you would be inhuman if you didn't have sympathy for her," he said.
"There's no dispute [the 14-year-old] caused Mr Kumar's death, and initially, some of you might harbour prejudice against [him] because of that."
However, the judge told the jury to focus on the "issues sheet" he had given them to avoid personal feelings and also warned them about a couple of witnesses.
Robert Watene, a transient Henderson man, said he had seen the boys sparring in the days leading up to the killing.
"That evidence is not going to assist you in determining what was in those young persons' minds at the critical times in the dairy," Justice Lang said.
Another teenager had followed the defendants to the dairy on the morning of the incident and gave evidence of what was said before and after the alleged murder.
But Justice Lang said his testimony must be approached with "considerable care".
The teen lied to police during his first interview and defence counsel said he was still lying to minimise his role in what happened.
Justice Lang told the jury if they acquitted the older defendant, his co-accused was automatically cleared. To convict him of manslaughter, they must be sure he and the 14-year-old had formulated a plan and that the co-accused knew serious physical violence was a probable outcome.
