The jury who considered the evidence in a murder trial never knew the "principal offender" was a patched member of the Head Hunters gang with more than 50 criminal convictions.

Tuale Joe Fuimaono, 28, was found not guilty of the murder of Bjorn Justin Henderson after a three-week trial in the High Court at Auckland, but guilty of the lesser charge of manslaughter.

Fuimaono, Ahmad Matlobyaygazwini and Ali Rafiee were sentenced by Justice Graham Lang to eight, seven and six years in prison respectively for their part in Mr Henderson's death in March last year.

The jury heard that Mr Henderson, a regular methamphetamine user, forcefully robbed Matlobyaygazwini of a large amount of P and cash from his Newmarket hotel room before fleeing to his Hamilton home.

A "furious" Matlobyaygazwini left a message on Mr Henderson's phone telling him he "didn't know who he had just ripped off" and warned: "You can't hide in Hamilton, it isn't a big place."

Mr Henderson was later lured to an address on the Ellerslie-Panmure Highway, then chased by Matlobyaygazwini, Rafiee - who was carrying a pistol - and Fuimaono.

The trio caught him and Fuimaono inflicted several heavy blows with a stick, the most serious a wound to the back of his head that caused his brain to bleed.

He was dumped at Auckland City Hospital but later died of his injuries.

After the trio were found guilty of manslaughter, Justice Lang sentenced Fuimaono to the longest sentence as he was the "principal offender" who struck the fatal blow.

The Herald can now reveal that Fuimaono, also known as Timothy Sasagi Vitale, is a patched member of the West Auckland chapter of the Head Hunters gang.

He has more than 50 convictions - including burglary, aggravated robbery, threatening to kill and methamphetamine offences - which Justice Lang took into account as an aggravating feature during sentencing.

But evidence showing a link to the Head Hunters, including a photo of Rafiee in gang regalia, was not shown to the jury because it was considered prejudicial to the accused.

A prostitute giving evidence in the trial was also put into the witness protection programme because of the possible threat from members of the Head Hunters gang.

The Herald was granted access to the court file but the photos were removed because Justice Lang said they were "irrelevant" to the trial and sentencing.

The Government has introduced new laws this year to crack down on gangs and the $1 billion methamphetamine trade, including the Criminal Proceeds (Recovery) Act, which allows police to seize assets and unexplained wealth from suspected criminals

Detective Senior Sergeant Hayden Mander, the head of the Operation Liverpool homicide inquiry, declined to comment on the links between gangs, P and violent crime.

But regardless of the circumstances - and who was involved - Mr Mander said every death needed to be investigated fully.

"If people are culpable for that death, they need to be brought before the courts. From the police point of view, it doesn't matter who the victim is. If a death has occurred, we need to get to the bottom of it."

Justice Minister Simon Power said gang membership could be admissible as evidence if it was considered relevant to the charge, for example if the accused was on trial for participating in an organised criminal group.

Recent amendments to the Sentencing Act, part of the Gangs and Organised Crime Bill, made gang membership an aggravating factor when it came to sentencing.