Revealed: The New Zealand regions with higher conviction rates for cannabis possession

A "postcode lottery".

That's how the New Zealand Drug Foundation has described police discretion over cannabis possession after their analysis showed users were more likely to be convicted depending on where they lived.

But Police says there are complex socio-economic issues to consider.

The NZ Drug Foundation analysed Ministry of Justice conviction data for cannabis possession from the past five years.

The analysis showed that, per capita, people on the East Coast were convicted at about three times the rate of those in the Auckland region.

It was a similar story in the Bay of Plenty and Northland, where people were convicted at more than two-and-a-half times the rate of the Auckland region, according to the NZ Drug Foundation's analysis. 

And that's despite similar levels of cannabis use prevalence across the country, according to the NZ Health Survey. 

"We do have a postcode lottery, really," NZ Drug Foundation executive director Sarah Helm told Newshub, referring to the organisation's analysis. 

But NZ Police Assistant Commissioner Bruce O'Brien told Newshub there were "likely to be a range of complex socio-economic issues that underlie the higher conviction rates in the Eastern, Bay of Plenty, and Northland districts". 

"Just because drug possession convictions in one district are higher than another doesn't mean that district policing is the underlying cause," Asst Cmmr O'Brien said. 

"Police's own analysis showed that the age of the offender, their prior offending history, and the frequency and severity of an individual's offending were more strongly linked to enforcement actions taken by police than any other factor (such as police district)."

Police say the Government's 2019 law change specifying that officers should use their judgement and consider a 'health approach' over prosecution for possession and use of illegal recreational drugs like cannabis, is making a difference.

Asst Cmmr O'Brien said there had been a "significant increase" in warnings for personal drug possession and use offences, and a decrease in the overall number of prosecutions. 

Police Minister Chris Hipkins told Newshub there could be "a number of reasons why conviction rates vary from region to region, for example respective cannabis consumption rates, amounts found in possession, frequency of offending or the number of previous warnings, but I have not seen any recent detailed analysis".

He also pointed out that conviction rates for cannabis possession "have come down significantly" - roughly 50 percent since the 2019 law change.

But that's not good enough for the NZ Drug Foundation.

"We had a thousand New Zealanders convicted in the past year," Helm told Newshub. 

Helm is worried that police discretion is not being applied evenly across the motu - a concern shared by drug researcher Chris Wilkins from Massey University's College of Health.

"We're putting a lot on individual police officers to make this call and it's quite an important call because it really does affect people's lives," Wilkins told Newshub.

"A conviction lasts for their entire life."

Asst Cmmr O'Brien said police will "continue to conduct analysis on this topic and will have updated analysis in early 2023".