A methamphetamine cook-up deal that soured was the catalyst for the brutal murders of uncle and nephew Raymond and James Fleet, a jury in the High Court at Rotorua has heard.

This was the assertion of Crown prosecutor Duncan McWilliam when he opened the double murder trial against Mikaere James Hura 21, and Zen Pulemoana, 27 
today.

The pair are on trail for the murders of both Fleets at Mamaku on August 7 last year.

They have been charged jointly with Martin Hone who, the jury was told, has already pleaded guilty to the charges. They also learned another man named during the Crown's opening, Richard Te Kani, has pleaded guilty to manslaughter.

Hura and Pulemoana have denied the murder charges and there have been not guilty pleas from Hura to three methamphetamine-related charges: intentionally possessing precursors and other materials, as well as possessing equipment for the drug's manufacture.

McWilliam outlined how Raymond Fleet had been manufacturing methamphetamine for others who suspected he was ripping them off because he wasn't delivering the amount they expected.

McWilliam said when the anticipated amount wasn't forthcoming, Hone became angry, paranoid and issued threats of violence that ultimately led to the murders.

He described how Raymond Fleet was attacked over the head with a spade, crushing his skull. When James Fleet saw what was happening he too was attacked.

"James was in the wrong place at the wrong time, he had seen too much and was killed," McWilliam said.

He described how some hours before his death, Raymond Fleet had been taken to Mamaku's remote Cecil Rd where there was a conversation, "not a polite one", about the methamphetamine that Hone believed was missing for the first batch Fleet produced.

After the spade attack Fleet dropped to the ground and his head was driven over causing massive crushing to his skull and brain.

"The Crown says James Fleet became a problem, evidence will suggest he was struck by Martin Hone on the back of the head causing two injuries, one fatal." McWilliam said.

He told the jury they would hear from a leading pathologist that apart from industrial accidents and car smashes, Raymond Fleet's injuries were the worst he had seen. Their severity meant he was unable to say whether Raymond Fleet's skull fracture had been caused by a spade or a vehicle.

James Fleet had died from blunt force trauma after suffering two severe wounds to the back of his head consistent with a spade being wielded in a chopping motion. One of these injuries had been fatal.

He described how the younger Fleet had earlier been severely beaten in the back seat of Bighorn 4 wheel drive.

Some time after the bodies were initially left where the fatal attacks occurred, they were taken further into the bush and rudimentary attempts made to cover them. It wasn't until 10 days later that police discovered them.

The Crown's case was that either Hone or Hura, who was present, drove over Raymond Fleet's head, if Hura had, he was guilty of murder as the principal offender or alternatively, if it was Hone who drove over the injured man, Huna was still guilty of murder by being a party to Hone's actions.

"These are both ways to convict him," the prosecutor claimed, saying at the very least Huna could be found guilty of manslaughter.

He urged the jury to find Pulemoana guilty of the murder charges as a party to the offending, pointing out he'd been present throughout the day that culminated in the murders. It was the Crown's contention his role had been an act of encouragement to Hura and Hone.

Making a brief opening statement for Hura, Harry Edward said the killings occurred under a backdrop of gang sub-culture.

"There is a hierarchy of which Hura is at the very bottom . . . there are rules in this sub culture, he was the gofer . . . had no control of these [methamphetamine-related] items."

He urged the jury to acquit Hura on all counts.

For Pulemoana, lawyer Max Simpkins said when Hone went into an uncontrollable rage Pulemoana was powerless to do anything. He urged the jury to acquit him on the grounds that he'd merely been present, not taken an active role in the killings making him not guilty or either murder or manslaughter.

The trial, which is expected to run for at least three weeks, is before Justice Sally Fitzgerald.