A 2019 change to drug laws has led to far fewer people being charged for drug use/possession, but Māori are now even more likely to be charged than non-Māori.
The trends are revealed in police data, released under the Official Information Act, which include a breakdown of how the law is applied in each police district for different ethnic groups.
It has led to allegations of "racist outcomes" - especially in the Canterbury and the Waikato regions.
Police deny this, saying that the most important factor in whether someone is charged is prior convictions - but they have provided no data to support this.
Parliament was warned when the law was passed that it could have a negative impact on Māori because putting police discretion into the law would also entrench police bias - conscious or unconscious.
Before the law change, Māori nationwide were 24 per cent more likely than non-Māori to be charged for drug use/possession.
Since the election, this has grown to 41 per cent.
The way police deal with cannabis use/possession is the main reason for the jump.
Twenty per cent of non-Māori were charged for cannabis use/possession before the law change, compared to 24 per cent of Māori. But since the election, the gap has ballooned: 8.8 per cent for non-Māori, and 15 per cent for Māori.
The data also highlights the postcode lottery of how discretion is used.
Since the election, a person caught with drugs in the Southern district has a 1 in 17 chance of being charged with drug use/possession.
Those odds jump to more than one in four in the Auckland City, Eastern (including Hawke's Bay and Tairawhiti) and Bay of Plenty districts.
The Government has ruled out any major drug law reforms this parliamentary term, despite calls for an overhaul of the Misuse of Drugs Act by dozens of health and social services.
That means it is unlikely the Government will replace police discretion with something less open to discriminatory outcomes such as mandatory cautioning - which was recommended in a 2011 Law Commission review.
Far fewer people charged
The Herald has been tracking police use of discretion following the 2019 law change, which clarified that police shouldn't prosecute for drug use if a therapeutic approach would be "more beneficial to the public interest".
People are often charged with drug use/possession along with other offences, so a better picture of the use of discretion is captured when that is the most serious offence - which includes when it is the only offence.
Police can choose to charge, warn, or use an alternative measure such as family group conferences, alternative action plans, community justice panels or no further action.
Trends in police behaviour can be seen by grouping the data into three time periods: the 12 months before the law change, the 15 months afterwards, and the seven months after the election and cannabis referendum.
That was when Health Minister Andrew Little clarified that someone should almost automatically get a health referral if facing a drug use/possession charge as their most serious offence. This contrasts with ministers' messages when the law was passed, when they denied it amounted to effective decriminalisation.
Before the law change, police laid charges for a third of the people they caught with drugs where use/possession was their most serious offence.
For the 15 months after the law change, that dropped to just under a quarter, and for the seven months since the election, the rate fell to fewer than one in five people (18.5 per cent).
The proportion of those charged with cannabis use/possession has roughly halved to 11 per cent since before the law change.
And for methamphetamine use/possession, it has fallen from 92 per cent before the law change to 55 per cent since the election.
Canterbury cops were the most likely to lay drug use/possession charges before the law change, when 46.3 per cent of those who might be charged were actually charged.
This proportion fell sharply to 24 per cent since the election, but the outcomes are becoming increasingly inequitable.
Māori in Canterbury were 33 per cent more likely to be charged than non-Māori before the change, but this jumped to more than twice as likely after the election. For cannabis use/possession, it's three times as likely.
Waikato cops follow those in Canterbury as charging Māori at far higher rates than non-Māori for drug use/possession since the election - almost two (18 per cent) to one (9.5 per cent).
The next districts where the outcomes are the most inequitable are Eastern, Wellington, and Northland.
The most equitable outcomes have been in the Southern, Tasman, Waitemata, Auckland City, Counties/Manukau, and Central police districts.
The data reveals the impact of the law change at the coalface, but nothing definitive about the reasons behind how discretion is applied, which inevitably involves many variables.
Te Pati Māori co-leader Rawiri Waititi didn't hesitate to pinpoint racism.
"We know that police are racist and we've been saying that for a long time," he said.
"It's a systemic issue that needs urgent addressing, for the sake of our whānau."
He called for what several independent reviews of the justice system have called for: an overhaul of the justice system towards a restorative and rehabilitative approach, based on tikanga Māori.
Drug Foundation executive director Sarah Helm said the 2019 law change had led to some improvements, but "inherent bias" in police discretion made it "unequal and unfair".
"However you slice it, overall discretion appears to be leading to racist outcomes."
Helm called for all drug use to be decriminalised, which the Government has ruled out, saying it would disrespect the result of last year's referendum on legalising cannabis for personal use.
She said convictions did nothing to deter drug use, a claim supported by the chief science advisor-led research into cannabis use, which found that 95 per cent of users "either continue or increase their cannabis use after arrest or conviction".
In a statement, a police spokesperson said it was inaccurate "from a statistical perspective" to suggest that a particular ethnicity from a particular district are more likely to be charged for drug use/possession.
"When all supporting information is assessed in relation to drug use/possession offending, 'ethnicity' and 'district' are neither predictive or key in determining whether a person is more likely to be proceeded against.
"Our own analysis shows that a person's prior offending history is the most important factor."
Police responded to a request to see its analysis by saying "we are currently compiling the data requested and we intend to publish the material within the next two months".
The Herald then requested this analysis under the Official Information Act, and police have pushed out the deadline for a response, saying it "cannot reasonably be made within the original time limit".
Most likely and least likely places to be charged
Post-election, Auckland City police are the most likely to charge for drug use/possession, with 28 per cent of people facing the possibility of such action actually being charged.
They are followed by Eastern (27 per cent), Bay of Plenty (26 per cent) and Canterbury (24 per cent).
The Herald previously reported that police in the Eastern District were most likely to charge people for drug use/possession, but at the time this was based on data over a shorter time period.
Cops in the Southern and Tasman districts are the least likely to charge people for drug use/possession, with the impact of the law being strongest in the Southern district; 19.8 per cent were charged before the law change, but this has fallen sharply to 5.9 per cent since the election.
In Tasman, as well as Waitemata, Counties/Manukau and the Waikato, the proportion of those charged has more than halved since the law change.
The change has had the least impact on charging tendencies for cops in Auckland City, where people are now far more likely to be charged than in neighbouring Waitemata and Counties-Manukau.
There seems to be no correlation between the ethnic make-up of the adult population in police districts and how the law is being applied.
The adult populations of the Northern, Eastern and Bay of Plenty police districts have the highest proportion of Māori, but none of the outcomes in these districts are at the far end of the equity spectrum.
Canterbury and Southern are at opposite ends of the equity spectrum, but they both have the lowest proportion of Māori in their adult populations.
Police diversity in each district also doesn't appear to correlate with how the law was being applied; Canterbury and Southern also both have the lowest proportion of Māori in their constabulary workforces (9 per cent).
Increasing diversity in the police force is part of Labour's election manifesto, and tackling police bias is something Police Minister Poto Williams has previously said was a major focus of hers.
Williams declined to comment on the latest data, as did Police Association president Chris Cahill.
A spokesperson for Little said the Health Minister, who is responsible for the legislation, was too busy dealing with the Delta outbreak to be interviewed.
Little is awaiting a review of the 2019 law change that was due last month, but it has been pushed back due to battling the current outbreak.
- Additional reporting and graphics: Keith Ng