Testing times for drivers: National’s new drug-driving law won’t detect impaired drivers & could see innocents prosecuted


The Government has confirmed they will “roll out” legislation this year to enable police to randomly test the saliva of drivers using inaccurate swabs that could see thousands of people subjected to roadside blood tests and prosecuted with no evidence of impairment. Here’s why the policy won’t make our roads safer, and why you should be concerned – this week on 95bFM’s Marijuana Media with Chris Fowlie from NORML and Milly from bFM Drive – thanks to The Hempstore!

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Let us start by saying no one should be driving while impaired. We all want safe roads and safe drivers. NORML has long said the responsible cannabis consumer does not operate a motor vehicle or other dangerous machinery impaired by cannabis, nor (like other responsible citizens) impaired by any other substance or condition, including some medicines and fatigue.

Instead of randomly testing 50,000 drivers using inaccurate saliva swabs which deliver false positives and are not actually calibrated to detect impaired drivers, a tech-based approach would be more effective, and cannabis legalisation could make our roads safer while balancing the budget and saving thousands of public-sector jobs.

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Residual levels of cannabinoids are not correlated to, or predictive of, impairment

The oral devices don’t show impairment, and neither does a blood test.

The law sets an arbitrary per se limit of, for cannabis, in either fluid of 1ng for a fine and 3ng for criminal prosecution – but a recent study found the detection of THC or its metabolites in bodily fluids is not correlated with impairment.

The literature review by UC Davis researchers, published in the Journal of AOAC (the Association of Official Analytical Chemists) International, said this includes blood, breath, urine, or saliva.

Researchers concluded that there is “no direct relationship between impairment and THC concentrations” in subjects’ bodily fluids.

“Current methods that focus on THC and/or metabolite concentrations in blood, saliva, urine, or exhaled breath can lead to false-positive results for recent use due to the persistence of THC well outside of the typical 3-4-hour window of potential impairment following cannabis inhalation.”

That conclusion is consistent with numerous studies reporting that neither the detection of THC nor its metabolites in blood, saliva or other bodily fluids is predictive of impaired driving performance.

Saliva testing of drivers is already allowed

Despite the evidence, the law already allows saliva testing of drivers. The Land Transport (Drug Driving) Amendment Act 2022 was passed by Labour with the support of every other party including National, and with only the Greens opposing it.

The main justification, still routinely cited by now-Transport Minister Simeon Brown, is that drivers in New Zealand impaired by drugs now cause as many deaths as drunk drivers.

The analysis by ESR is junk science. They counted drivers with any trace of illicit drugs (not just those who were impaired), but ESR only included drunk drivers who were over the legal limit (ignoring potentially many more who were impaired but below the limit). Curiously, the US says 25% of road deaths involve alcohol or drugs, half of ESR’s claimed rate here.

Nevertheless, the law took effect last year and creates an offence for driving with a qualifying substance in blood or saliva.

They’re not trying to detect impairment

The offence is not actually being impaired on the road. The offence is another version of drug possession (in bodily fluids). This could be yet another criminalisation of non-problematic drug use.

The expert committee charged with setting an impairment threshold for “qualifying substances” in bodily fluids could not find evidence that any number would show impairment so just went with two arbitrary figures which they claimed would instead show recent use:

  • 1ng/ml in either blood or saliva is deemed to be ‘low risk’ and would get a fine and demerit points;
  • 3ng/ml is apparently ‘high risk’ and would lead to criminal proceedings.

The two-tiered penalties are aligned with the approach to drunk driving. But there is no evidence to support how those figures were chosen.

The law was amended so references to impairment are now references to recent use. But the available evidence suggests that regular cannabis users – which would include most medicinal users – can have higher levels for days after cessation, long after any impairing effects have worn off.

Existing oral devices are all unreliable

Much to the chagrin of police and the National Party, the existing law requires oral devices be accurate to an evidential standard. But the available devices are not reliable and can’t be used in proceedings.

Australia has used oral test devices for several years as a screening tool. An estimated 20 per cent of tested drivers are either falsely accused of being impaired, or are impaired but not detected.

This was known at the time our law was passed. So, our law bizarrely requires a driver fails two oral devices – because failing one cannot be trusted with any certainty.

Our police haven’t been using them, instead using Compulsory Impairment Tests (walk a straight line, etc) and blood tests if they have cause.

A small change with big, unexpected consequences

Following a request from Police and MoT officials, a briefing paper had gone to Kiri Allen & Ginny Anderson last May and was approved by Labour’s cabinet. Their cabinet paper says it would require a law change, which has now been picked up by National.

Transport Minister Simeon Brown says he will amend the existing law by the end of this year. This will enable the oral swabs to be used to randomly test any driver, with a subsequent blood test used as evidence. He expects police to randomly test the saliva of 50,000 drivers every year.

This small legislative change will have big consequences. But the result won’t be the promised gains in road safety, but the unintended prosecutions of potentially thousands of innocent drivers.

The change will let police randomly use oral swab devices (known to be inaccurate) to trigger a compulsory roadside blood test (by force if necessary) which will have no relation to, or predictive power of, any level of impairment by the driver.

This will align our law with Australia, where people are routinely prosecuted for inactive metabolites or low residual levels that are not indicative of impairment.

Like in Australia, our Police will waste a huge amount of time and effort erroneously testing and prosecuting drivers who aren’t impaired, while missing a significant chunk of those who are impaired, therefore failing to achieve the stated objectives of the policy.

Another Australian phenomenon we can expect to see: the middle classes and wealthy using Ubers to get everywhere, while those who can’t afford to do that will be subject to intrusive roadside testing.

Your own phone could do a better job

Police could use a test that actually detects impairment – such as a tech-based approach like the DRUID app or the Alertometer app now used by livestock truckers with the blessing of Waka Kotahi.

These can be installed on a typical smartphone and used before a shift or safety-related task such as driving. The app measures responses to visual and other prompts in a game-like way and compares this to a user’s baseline data gathered using the sensors embedded in the phones we all carry.

This is the 21st Century approach but oral swabs seem so… 1950s.

The medical defence

The good news is that New Zealand drivers, unlike Australia, have a medical defence.

A driver prescribed medicinal cannabis – or any other prescription medicine including pain meds and sleeping pills and whatever else you’re on – has a defence to proceedings as long as they’re following their doctor’s instructions.

Typically, that may be “Don’t drive for 4 hours after use.” This is very good advice. It is more accurate than saliva tests, and another reason to get a prescription.

In other news: more medical cannabis products approved

Newly available here, from Australian Natural Therapeutics Group, ANTG Rocky Oil is high THC (30 mg/ml), Luna Oil is balanced THC 10 to CBD 10, Eve Oil is CBD-only at 50mg/ml and Elan Oil is twice the strength at 100mg/ml CBD.

Meanwhile from Medleaf a new flower for tea, Orange Kush C, 21% THC in 30g packs. In NZ any doctor can prescribe cannabis for any reason. See the MOH’s list of approved products and my guide to accessing medicinal cannabis in NZ.

Analysis: THC dosing associated with increased survival time in palliative cancer patients

The daily use of 4.7mg of THC was associated with significantly increased survival times in palliative cancer patients, whereas lower doses were not, according to data published in the journal Medical Cannabis and Cannabinoids.

German researchers evaluated the impact of THC dosing in a cohort of 9,419 advanced cancer patients enrolled in Specialized Palliative Outpatient Care.

The study concluded “Median survival time was prolonged by 15 days – from survival time of 25 days without THC therapy to 40 days with a daily THC dose higher than 4.7 mg per day. This prolongation by more than two weeks can be considered substantial. In addition to mere survival, patients [treated] with THC become more mentally and physically active. … The increased activity and improved quality of life might enable the patients to renew social contact with relatives and friends and to settle essential affairs before dying.”

Study: Cannabis extracts reduce disease burden in chronic pain patients

Haifa, Israel: Patients’ use of cannabis oil extracts is associated with long-term improvements in their pain intensity and related symptoms, according to data published in the journal Pain Reports.

“Cannabis seems to have an impact on the ‘disease burden’ of chronic pain,” the study’s authors concluded. “It also has a positive effect on functioning and health-related quality of life.”

Stuff: Fund my cannabis medicine: Man’s plea to ACC.

Evan Harding writes about Toni Jarvis wants ACC to pay for cannabis medication which he says helps him deal with the mental health issues he has as a result of being abused in state care. After initially refusing, ACC had a change of heart.

International: White House endorses marijuana rescheduling plan; says cannabis’ placement as a Schedule I substance “just doesn’t add up”.

Schedule III is less illegal, but not legal. The Independent called it a “historic shift”, the BBC noted Biden slammed the ‘failed approach’, while NORML says it doesn’t go far enough.

The Conversation: Aussie researchers say legal cannabis needs to be cheap

“Otherwise, legalisation might not deny profits to organised crime – or deliver a substantial tax windfall – after all.”

They estimate daily and weekly cannabis users account for 98% of consumption of the market, estimated 441 tonnes, even though they are just 36% of cannabis users.

“To reduce illegal trade, a new legal market must attract these users”. Daily or weekly users typically buy in bulk and pay cheaper rates per gram. If cannabis is sold at an excessively taxed rate, those consumers will stick with unlicensed suppliers.

The researchers’ new “credible estimate” is A$13 billion tax revenue, with prices based on A$300 ounces and 20% tax.

Adjusting this estimate for New Zealand is NZ$2.8 billion tax revenue on an estimated 87 tonnes.

Balance the books with legal cannabis

That “credible estimate” shows legal cannabis could fund the budget deficit and negate the public sector layoffs.

Our Prime Minister and Minister of Finance are looking for $1.5 billion to fund their tax cuts and other policies. They’re doing it through austerity and firing thousands of workers. But legal cannabis would raise almost twice that!

Legal cannabis is also associated with safer roads. A new analysis shows fewer young adults driving impaired following cannabis legalisation. According to data published in the journal Prevention Science, the legalisation of marijuana in Washington state was not associated with any uptick in the percentage of young people driving under the influence of either cannabis or alcohol.

National’s new fact-free approach to drug driving ignores the evidence and won’t detect impaired drivers. Their continued adherence to prohibitionist ideals is a lost opportunity to make New Zealand safer while also balancing the books without needing to fire thousands of skilled and valued public sector employees.

Legalise cannabis to save your job!

Cannabis friendly events:

  • Whakamana medical cannabis social club, Thursday evenings at the Blue Frog (Silo Park)
  • Substance checking at The Hempstore, Saturday 1st June (11am-3pm)
  • High Art photography exhibition by Heyley Theyers, at The Hempstore, opening on ‘First Thursday’ 6 June 5-8pm, then runs til 27 June
  • Auckland J Day Saturday 7th December 2024



Marijuana Media airs every Thursday at 4:20pm on 95bFM, with bFM Drive’s Milly and Chris Fowlie from The Hempstore. Stream or download hundreds of Marijuana Media pot-casts at 95bFM.com (or via iTunes / RSS feed). Thanks to The Hemp Store!



  1. This, has nothing at all to do with road safety and everything to do with normalising authoritarianism. It’s a softening up process for tighter controls over our general freedoms of being able to come and go where ever we like at any time. My personal opinion is that the squeaky mouse initiative has more to do with the likely resistance to what looks like the U$A Military industrial complex’s plans to turn us into a missile launching pad.
    The natzo’s clearly don’t care about us otherwise there wouldn’t be 600,000 people in poverty and 200,000 kids going hungry while our politicians greedily grasp the six figures plus entitlements they make sure we must pay them. We’re heading into scary, fascist-authoritarian times in my opinion. Again, in my opinion, we should resist. Just say no.

  2. 6 Yeats in power and Labour could not come up with a driver’s drug test 6 months in power and National has .This is just one sign of how proactive National is .

    • Please read Martyn’s column, your stupid adulation of National and this policy without a clue as to the cost to reward ratio, knows no bounds, like every other one of your posts.

      • Martyn finds fault with every move Nationsl make.No plaudits for money to I am hope or lifesaving.
        The story is always the same .It all boils done to landlords getting a tax break by this government when all they did is return the status quo that held good for 128 years until Robinson intervened.
        To my mind anyone who drives after drinking or smoking weed is a menace and should be dealt with.

      • NSC you may wish to reread your comments then issue an amendment,as it stands it makes no sense.

        • Well I wouldn’t expect someone with such a low IQ as you to understand such an eloquent and intelligent post such as mine, but I do enjoy your trolling of me. Thank you, my number one fan.

  3. The developed world has moved on from reefer madness and started decriminalizing if not legalizing this drug, such as our Australian cousins. Once legal (adults can grow their own or buy cannabis in a store and consume it in their residence) people could just self police their use as they do with alcohol, notwithstanding the impairment from weed when operating heavy machinery is orders of magnitude less than drunkenness. Or should we ban alcohol because of its (self policed) horrific outcomes? If it’s the taxes the government is worried about then a legal cannabis market would surely deliver an order of magnitude greater return than the benefits (waste) from chasing recreational users. If it’s public harm that they want to reduce, then they should concentrate on testing meth zombies and recalcitrant pissheads.

  4. The law is an ass and the plods are donkey’s dicks. What’s new?
    Grow and smoke with the same laissez-faire, blaise attitude as when you know you’re speeding 5k over the limit in the safe knowledge any conviction on your record is getting expunged on legalization day.

  5. “responsible cannabis consumer does not operate a motor vehicle or other dangerous machinery impaired by cannabis” Unfortunately in any large enough group there is always a percentage of fuckwits.

  6. Here’s an idea, gather some funds, get a good lawyer & test it in court. See how that works out.

  7. While you appear to have a legitimate case regarding the proposed drug testing methods it’s a pity that you didn’t spend at least some of your time encouraging people to actually eat healthy food & live a clean lifestyle so they did not require chemical substances to reduce problem pain in their life. I know that my kind of thinking will not be popular with the “if it feels good then do it crowd” but since I would presume that you would know that the thrill of flying through the air is not enough to compensate for the impact on landing which is why we have regulations around things like bungy jumping, sky diving, high buildings & bridges, etc. I would hope that encouraging people to look after themself would be viewed as a positive thing to do which people do voluntarily as the moment any do-gooder government tries to force it upon the population you can be sure that the cure will probably be worse than the disease.

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