A new device being developed in the United States could change the way cannabis use is policed on the road.
Researchers at Virginia Commonwealth University are working on a “cannabis breathalyser” capable of detecting THC – the psychoactive component in marijuana – within a recent-use window.
The goal is to create a device similar to alcohol breath tests, a roadside tool that can indicate whether a driver may be impaired.
Dr Teresa Nicoletti, a scientist and lawyer who specialises in the regulation of medicinal cannabis, says there are practical and legal barries to bringing this technology to Australia.
“The question isn’t whether you can detect THC,” she says.
“The question is whether there is a reliable impairment window.”
Currently, saliva tests can detect cannabis long after its effects have worn off. In all Australian states (except Tasmania) it is a criminal offence to drive with any detectable THC in saliva, blood, or urine even with a medical prescription.
The Alcohol and Drug Fundation says roadside drug testing “focuses on detection rather than impairment”.
“This means you can be charged when certain drugs are present in your system, even if you don’t feel intoxicated and it’s been a while since you last used the drug.”
But Australian authorities are softening their stance.
NSW Premier Chris Minns said in February that his state was examining changes to laws surrounding cannabis detection and driving.
“Hundreds of thousands of people are accessing it as a legitimate health alternative to even more powerful drugs,” he said.
“We need a fit-for-purpose regime on NSW roads so we’re not disenfranchising people. We will draft our own legislation, but we’re actively considering a change in the policy.”
A reader poll asking attached to our report of that news asked “Should medicinal cannabis be exempt from drug driving offences in Australia?”, and found 63 per cent of more than 5000 responses said “yes”.
The Victorian Government is currently running a world-first trial to measure the effect medicinal cannabis has on driving behaviour.
Run by Swinburne University, the trial puts participants behind the wheel of a car in controlled closed-tract conditions with road features such as traffic lights, before and after they consume medicinal cannabis.
Swinburne University says “the outcomes of this study will add to the data and knowledge needed to determine if Victorians who are prescribed medicinal cannabis (containing THC) can be in control of a vehicle without compromising their safety or the safety of other road users”.
The binary, all-or-nothing approach by Australian legislators has increasingly come under scrutiny, particularly since medicinal cannabis was legalised in 2016.
“It doesn’t make any sense,” Dr Nicoletti says. “You’ve legalised medicinal cannabis at a federal level, but then effectively blocked its use at a state level through road laws.”
The appeal of a breathalyser is clear.
A test that focuses on recent use rather than lingering traces could, in theory, offer a fairer system.
But that depends on whether recent use can actually be linked to impairment in a meaningful way. Cannabis can affect individuals very differently. Factors like dosage, frequency of use, and a person’s own biology all play a role.
“How THC affects someone depends on how it’s absorbed, how their endocannabinoid system responds, and whether they’ve built up a tolerance,” Dr Nicoletti says.
“You can measure THC in blood, but that concentration does not equate to impairment,” she says.
That’s where Dr Nicoletti sees a problem with the way cannabis breathalysers are being framed.
“They’ve put the cart before the horse,” she says.
“What is the impairment window? It hasn’t been defined.”
Any innovations in this sector would also have to navigate Australia’s fragmented legal system. Road laws are set at a state level, meaning reforms would need to be adopted jurisdiction by jurisdiction. Several attempts to introduce exemptions or update the rules for medicinal cannabis patients have already been made, to little effect.
“I don’t understand the barrier,” Dr Nicoletti says.
“There have been bills tabled before parliament, and they’ve gone nowhere.”
Enforcement works in a system that can detect cannabis, but doesn’t distinguish between past use and present impairment. Magistrates, Dr Nicoletti says, are often left dealing with the consequences, sometimes showing sympathy within the limits of the law.
“There are very sympathetic magistrates who are also frustrated by the legislation and the strict liability offence that arises with someone detecting positive to THC,” she says.
“There is frustration in the judiciary as well.”
As new technologies offer new and more accurate ways to detect cannabis, the legal and scientific frameworks needed to interpret those results remain unsettled.
The creators of the cannabis breathalyser prototype in the US say “it is vital to create and improve technologies for its detection in a fast, reliable, and in situ method for public safety and awareness”.
– with David McCowen
