How high is too high? Roadside marijuana testing faces challenges ahead of legalization

As we speak, researchers are working hard to develop a roadside test for marijuana intoxication, and with the science getting closer to perfecting a workable version of the “potalyzer,” next year’s legalization of cannabis in Canada could mean a huge jump in the number of arrests for drug-impaired driving.

But one questions remains. When it comes to driving while under the influence of marijuana, how high is too high?

Public Safety Canada just released the findings from its Oral Fluid Screening Device Pilot Project, aimed at trying out two different saliva-based, roadside tests for drug intoxication. The project involved seven police jurisdictions across Canada over a four-month period, with officers being trained in administering the tests and trying them out in the field (drivers submitted saliva samples voluntarily and were not held to any charges stemming from the tests).

Results from the pilot showed that of 1141 oral fluid samples taken, about 15 per cent delivered a positive drug reading, with cannabis being the most commonly detected drug. And while police officers raised some concerns over the durability of the testing devices, the overall conclusion was positive.

“With the proper training and standard operating procedures, these devices are a useful additional tool for Canadian law enforcement to better detect individuals who drive under the influence of drugs,” reads the report.

The pharmacological load [for marijuana] doesn’t connect with the level of impairment as closely as it does with alcohol,” says Jones. “You can have people with high doses of cannabis who have a low level of actual impairment and some others with a low dose who are significantly impaired…

Yet, the issue of testing for pot intoxication is a tricky one, in part because drug-impaired driving itself is becoming more of a challenge for law enforcement.

As reported by CBC News, a study by the Canadian Centre on Substance Abuse found that the percentage of drivers involved in fatal collisions who tested positive for drugs rose from 29.7 per cent in 2000 to 36.7 in 2008. And at a time when the overall rate of impaired driving has fallen in Canada, drug-impaired driving offences have quickly spiked, with Statistics Canada reporting 183 charges in 2008 compared to 1,159 in 2013.

Much of that rise has to do with increased police powers to enforce impaired driving laws. Changes to the Criminal Code in 2008 gave law enforcement the authority to submit drivers to the Standardized Field Sobriety Test (SFST), to provide a blood, urine or fluid sample or to be evaluated by a Drug Recognition Evaluator, all of which have contributed to more charges and arrests.

But the introduction of a roadside, point-of-contact drug screening device will be a real game changer. Less resource-intensive than blood or urine tests (which require taking the driver to a testing site), saliva sampling is also a better gauge of recent drug use. Urine screening, for example, tests for drug metabolites whereas saliva tests identify the presence of active drugs in the system.

And thanks to the explosion of research around nano-sensor technology, testing devices have dramatically improved their accuracy in recent years, leading to their implementation in countries such as Australia, France and the United Kingdom.

Alcohol testing generates a high level of confidence, but we’re not there yet on drug testing. We also don’t want testing to let people who are drug-impaired keep driving because of a negative reading…

Even with much better detection tools, however, one big question remains: how high is too high? Notoriously, drug impairment is a less predictable phenomenon than alcohol impairment, which blood alcohol levels can determine to a fairly accurate degree. Not so much for drugs like marijuana, where the impact of a given amount of cannabis can produce widely different results in different people.

That’s a law enforcement concern to Craig Jones, Executive Director of Norml Canada, an advocacy group for marijuana users’ rights, who spoke with Cantech Letter.

“The pharmacological load [for marijuana] doesn’t connect with the level of impairment as closely as it does with alcohol,” says Jones. “You can have people with high doses of cannabis who have a low level of actual impairment and some others with a low dose who are significantly impaired.”

Jones sees the newness of the testing technology as part of the problem.

“The main concern is the likelihood of false positives,” says Jones. “Alcohol testing generates a high level of confidence, but we’re not there yet on drug testing. We also don’t want testing to let people who are drug-impaired keep driving because of a negative reading.”

Even with a positive test, however, the question will still need to be addressed concerning what will constitute the magic number: the legal limit for marijuana in the system. Although the blood alcohol level for drivers in Canada has been set at 0.08 per cent, that number varies from country to country, based on social norms and values. (Canada’s limit is actually high — 0.05 or less are more the norm in Europe, by comparison.)

Figuring out a similar amount for marijuana, while important not just for enforcement but also in deterrence, will be a challenge, says Doug Beirness, senior research associate for the Canadian Centre on Substance Abuse.

“That’s a daunting task,” says Beirness to CBC News. “It took us 50 years to come up with the level of 80 [milligrams of alcohol in 100 millilitres of blood] for alcohol. We don’t have the time to do that.”

The trick, says Beirness, will be to increase public awareness ahead of next year’s marijuana legislation of the dangers of driving while high.

“Young people between 15 and 24 don’t think cannabis use has any effect on driving, and that police can’t do anything about it,” says Beirness to the Ottawa Citizen. “We have to create a culture that doesn’t accept the use of cannabis and the operation of a motor vehicle.”

Jones echoes the point, saying that while he fully supports the ramping up of efforts to control drug-impaired driving, there’s “going to be a lot of trial and error” in enforcement over the next few years, which means that public awareness and education need to be placed front and centre, too.

“Anything to keep people safe on the roads is a good thing, and we’ve seen with alcohol and groups like Mothers Against Drunk Driving that public education works,” says Jones.