Canada’s recreational marijuana legislation which is set to go into effect in October includes a stringent DUI code, developed to appease those who were concerned that cannabis legalization would result in an increase in highway fatalities. Sister Bill C-46, which passed in June, includes a massive overhaul of Canada’s impaired driving laws.
However, to enforce that code, a reliable roadside test is needed to detect the use of cannabis. Canadian officials spent millions researching their options, with an independent committee of toxicologists and traffic safety experts put together to research available tools and make a recommendation.
A number of options were tested in a National Research Council laboratory and evaluated by the Canadian Society of Forensic Science. Also, Public Safety Canada and the RCMP initiated a study on oral fluid screening devices and concluded they were “a useful additional tool for Canadian law enforcement.”
A decision has finally been reached. Canada’s Justice Department, headed by Attorney General Jody Wilson-Raybould, is set to give its blessing to the Dräger DrugTest 5000 roadside saliva test. The device, which is produced by a company based in Germany, is already being used in the United Kingdom and Germany. (The Dräger device was not one of the two used in the RCMP study.)
The test involves swabbing a driver’s mouth to collect oral fluids to test for the presence of THC, the main psychoactive ingredient in cannabis. A positive result on the roadside test gives police reasonable grounds to detain the driver and require further testing, i.e., a blood test. The results of the blood test will then be examined by a drug recognition expert to make a final determination as to whether or not to press charges for DUI.
The law itself calls for “per se” limits for drug blood levels. What this means is that police can file criminal charges against a driver based solely on the level of THC in the blood with no actual proof of impairment.
According to a report, the federal government is budgeting $81 million for provinces and territories to buy the screening devices and to train officers in their use.
A Foolhardy Plan?
While tests for measuring alcohol blood levels have proven to be mostly reliable, there’s no such thing as a reliable test for impairment due to consumption of cannabis. Although roadside tests and blood tests may be able to determine that a driver is a cannabis consumer, they cannot be used to prove impairment.
Reports have been quick to point out some of the flaws in this system. As Scott Newman, a spokesperson for the Criminal Defense Lawyers Association of Manitoba, Canada, told one outlet: "There's no true, reliable way to test for the presence or absence of recent drug consumption… The saliva test doesn't really tell you a lot because the effects of marijuana can stay in the system of anyone up to 30 days."
If you’re an occasional user, saliva tests can detect THC for about 24 hours after consumption, and, depending on a variety of common factors (such as how often one brushes their teeth and which toothpaste they use) this can stretch to as long as 72 hours. And, if you were a heavy smoker but recently quit, saliva tests can produce a positive result for weeks after the last joint has been smoked. Even 24 hours is surely a sufficient passage of time for any impairment from THC to have worn off.
Furthermore, research has proven that other compounds found in cannabis, particularly cannabidiol (CBD), can significantly reduce the effects of THC, while others, such as a terpene known as myrcene, can greatly increase impairment. Theoretically, for a test to be even somewhat credible, it would have to test for CBD as well.
How THC Affects The Human Body
As an example, if a cannabis user has consumed 10 milligrams of THC over the past 24 hours, but has also consumed 100 milligrams of CBD. The level of impairment, in this case, would be impossible to predict. It would depend on factors which are outside of the realm of drug testing, including the expression of CB1 cannabinoid receptors in certain areas of the individual’s brain.
Aside from there being no perfect measure of impairment from cannabis use, the tests are easy to beat. Chemicals known as adulterants can be used to reduce THC levels in the saliva. For example, hydrogen peroxide is just one of many adulterants that can be used to skew results quickly. It would be fairly easy for a driver to keep one of these products handy in case of getting pulled over.
Also, according to one expert, “There are more important considerations when it comes to the ability to tell whether you’re a pothead. You have to take into account your body mass, your level of physical activity, age, metabolic rate, overall health, the level of your individual drug tolerance, the potency of the weed strain, and how much of it you smoked.”
The reliability of THC tests is likely to be challenged in court by defense lawyers who will easily poke holes in the results no matter which test is being used. Police in many U.S. states already use saliva testing and, according to Scott Newman, they rarely result in impaired driving convictions.