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Saliva Screening as an Effective Method for Cannabis Use Detection

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Read time: 3 minutes
At present, if a person appears to be driving under the influence of alcohol, or is suspected of drunk and disorderly behavior, law enforcement has many different methods at their disposal to assess how intoxicated that person may be. Blood and urine samples can be taken when a suspect arrives at a police station, and breathalyzers can be used at the roadside for a speedy, portable, and non-invasive test. With medicinal and/or recreational cannabis use becoming legal in a rising number of countries worldwide, it is important that there is similar infrastructure for drug impairment testing in place.

Testing for cannabis intoxication presents unique challenges when compared to the common alcohol tests. The behavior of cannabinoids in the human body means that blood and urine samples are not always representative of the level of intoxication, as traces of the drug remain in the body long after the intoxicating effects have worn off. For example, alcohol dissipates from the blood after 12 hours, with traces present in the urine up to 5 days later. Cannabis, on the other hand, can stay detectable in blood samples for up to two weeks, and in urine samples for twice that.

This means that regular cannabis users would be unable to pass traditional drug tests even if they were completely sober at the time the test was administered. This is a particular worry for some medicinal cannabis users, the majority of which take the drug in doses that are large enough to relieve their symptoms, but small enough that they don’t feel intoxicated or report any sort of impairment. The possibility of failing drug tests while driving or at work has made many people feel like they are being robbed of the independence they gained by being able to control their symptoms in the first place.

A more accurate intoxication test

Unlike alcohol, cannabinoids cannot be detected on the breath, so a breathalyzer system isn’t an option for detecting recent cannabis use. But according to Marilyn Huestis, the former Chief of Chemistry and Drug Metabolism for the National Institute on Drug Abuse, there may be another way.

Recent research conducted by Huestis, in partnership with Michael Smith of Huestis & Smith Toxicology LLC, concluded that the analysis of saliva could provide a more representative picture of a person’s recent cannabis use, even if they are a regular cannabis user. By analyzing the THC content of a saliva sample, they found that it is possible to accurately determine if someone has used cannabis via smoking, vaporization or ingestion of edibles, within the past 24 hours. It was also possible to distinguish recreational cannabis use from Sativex, a common CBD: THC medicinal cannabis oil when the test was administered within a few hours of taking the drug.

"I believe that we should be documenting impairment, and then we should be using oral fluid [as a testing marker]," said Huestis, in an interview with The Oregonian. "It's noninvasive, doesn't require medical personnel to draw it, it doesn't require a person to be stuck by a needle."

The road to implementation

Many countries are already using brands of saliva-based drug testing kits to test drivers that are suspected of driving under the influence. Scotland is due to roll out saliva-based roadside drug testing equipment in 2019, in a move that will match the current procedure in England and Wales. In Australia, this sort of roadside drug test has been commonplace for years.

Canada, which is set to federally legalize recreational cannabis in late-October, is also set to begin the roadside saliva screening of impaired drivers after Justice Minister Jody Wilson-Raybould approved the first piece of saliva screening equipment for use in the country. The judgment allows local law enforcement to choose whether they want to use the equipment alongside the standard visual field sobriety tests.

Despite the Justice Minister’s approval, not all of the legal professionals in Canada are convinced that the move is a good idea. Kyla Lee, a Vancouver-based criminal defense lawyer who specializes in impaired driving cases, believes that the use of the device could invite a lot of legal challenges against the state.

While the Dräger DrugTest 5000 system that has been approved for use is certainly much faster than taking the driver to the police station to submit to blood and urine testing, it certainly cannot match the speed of the roadside breathalyzer for alcohol. The device requires a 10 minute window before the test is administered where the driver does not eat or drink, then it can take several minutes to carry out the saliva collection and an additional 10 minutes for the device to analyze the sample.

"The problem is that roadside impairment testing is supposed to be done immediately which is not going to happen with this device," Lee explained to CBC News. "It's really out of step with what the courts have authorized insofar as roadside testing for impaired driving."

From a civil rights perspective, Lee also has concerns. Saliva samples contain an individual’s DNA and breath samples do not, which Lee sees as proof that these devices are very different to anything Canada has authorized previously.

"Saliva is very different,” Lee continues, ‘We're not all going around giving the police or government samples of our saliva."

Additionally, Canada hasn’t specified any limits on what levels should constitute as impairment from THC. Cannabis intoxication can be much harder to spot than alcohol intoxication as you can smell liquor on the breath of a drunk driver, but depending on the method of administration, there may not be any similar scent to detect with cannabis use. Minorities and people of color are already stopped at disproportionally higher rates for suspected drug offenses, and adding a DNA element into testing for a drug that is known to be hard to visually detect is something that must be done sensitively and with complete transparency. Local police forces that choose to use the saliva tests must reveal exactly how and when the saliva samples are disposed of.

"The Supreme Court of Canada is going to have to sort it out, which means millions of dollars and several years before we have an answer about whether or not this is actually something that should be taking place on our roadways."