A man found guilty of meth charges had months hacked off his sentence after he convinced West Auckland gang members to surrender a cache of 20 weapons including a military grenade and World War II machine gun.

Caleb Borrett was found guilty at trial of possessing 17.5gm of methamphetamine for supply and two counts of possessing cannabis.

The judge discounted his jail term by 15% in response to a number of mitigating factors including the police assistance, efforts at rehabilitation and voluntary work.

Police found the majority of the drugs, worth up to $14,000, hidden in a headboard of a bed in which he was sleeping at his family's Massey property.


Borrett was also in possession of two P pipes and nearly $1000 in cash.

He came before Auckland District Court last week knowing he faced a potential prison term but his lawyer Jonathan Krebs argued his assistance to the authorities should be recognised with a significant sentence discount.

The argument was made in the wake of a previous case in which a discount had been applied. In court, the Crown prosecutor noted police were concerned the practice was a "worrying trend".

In this case, Borrett had organised with West Auckland gang members to have 20 weapons given to the police.

They were finally handed in - using a former officer turned private investigator as intermediary - the day before sentencing last week.

Krebs said the negotiations had been ongoing for weeks and the court should not be cynical about the timing of the surrender.

The cache, which featured about 20 weapons, included a military grenade and a World War II machine gun which had been stolen in Christchurch in 2008, the court heard.

Crown prosecutor Hannah Clark said police believed some of the firearms were stolen and had serial numbers filed off.


She said police had voiced concerns about the practice of providing weapons for lighter sentences.

However, police later pulled back on that position, telling the Herald they were not aware of it becoming an increasing trend.

Police said they did not comment on court discussions regarding sentencing but cases of this nature were "rare".

Labour's justice spokeswoman Jacinda Ardern said she could not comment directly on decisions of the judiciary but it seemed counterintuitive to reward an offender for what appeared to be "more evidence of illegal activity".

"We've had amnesties before and if we can get illegal weapons out of the community that's a good outcome. But should there be an expectation anything's received in return? Most people in normal circumstances don't receive any reward for that," she said.

In a letter to the court, Borrett said he had no link to the weapons and had arranged for them to be given to police because "nothing good comes of having them".

His lawyer argued home detention would allow him to part ways with the criminal lifestyle.

"He's aware he's staring down the barrel of a prison sentence," Krebs said.

"But to send him to prison would be to send him into the company of others he's trying to distance himself from."

Clark was skeptical about Borrett's commitment to change and questioned how he could be so influential in the return of weapons if he had severed gang ties.

Despite that submission, Judge Anne Kiernan said it was important to recognise the defendant's actions.

"As a result, those weapons are not available and as a result, the community is safer," she said.

Judge Kiernan shaved six months off Borrett's jail term, but it was not enough to see it drop below the two-year threshold where home detention is available.

He was sentenced to two years 10 months.

Having previously been bailed to attend the birth of his first son, Borrett had to be dragged to the cells, telling guards "my kid's sick" as he struggled with them.

Police Association president Greg O'Connor rejected the police's official stance that this was an unusual case.

He said the association had been before a select committee to raise the issue of gangs storing caches of weapons for just the type of eventuality as in the Borrett case.

Members all over the country had told O'Connor the problem was not unique to Auckland too.

"Firearms were always expensive and hard to get, and that's why people didn't carry them that much. Now they're so easy to replace - every two-bit crook's got one," he said.