The passage of Bill C-46, which significantly changed Canada's impaired driving laws, heralded a new age for roadside regulations by allowing blood testing for drug impairment.

Why Canada’s new impaired driving laws fail when it comes to cannabis

The passage of Bill C-46, which significantly changed Canada’s impaired driving laws, heralded a new age for roadside regulations, following the lead of Europe, Australia, and New Zealand to allow blood testing for drug impairment (1).

A breathalyzer may still be used if you’re drunk, although a police officer simply saying you are impaired on drugs (2) will grant them the unwarranted freedom to screen you and anybody else they want while ensuring they find proof of intoxication through the most invasive bodily fluid they can.

Oral detection was supposed to make detecting impaired driving easier

For cannabis, oral detection was supposed to be a quick, noninvasive way to determine if the person has THC in their system or not (1, 3). We all cringe at the word “Draeger”, for different reasons, and the use of Draeger machines leaves Canadians stuck with a method that may not be as invasive but it comes at the expense of being highly unreliable.

These machine’s early trials were a surefire way to waste taxpayer dollars and it was a false chance for the public to avoid being detained and having their blood tested prematurely.

Preliminary laws were drafted which planned for oral fluid tests to determine initial detection, which is a noninvasive way to verify if a drug has been used before moving to extract bodily fluids from beneath your actual flesh. As various medicinal patients have agreed, blood extraction is far more likely to induce feelings of anxiety and stress.

But official requirements failed, so using saliva for drug testing was scrapped (4, 5.) because, in reality, these recommendations did not match up to practical needs (6.). The Draeger technology came with a variety of requirements that made it ill-prepared for use in Canada- such as the machine’s ideal operating temperature is between 5-35 degrees Celsius, which makes the machine basically useless during the winter.

Having THC in your system doesn’t automatically mean impairment

Bill C-46 also puts many patients and daily users of cannabis in legal jeopardy (7, 8, 9) since how recently cannabis was used cannot be determined by oral or even blood tests, (1, 3, 7, 10, 11, 13) as cannabis can stay in your blood, above the legal limit, for days and even weeks (12). Testing oral fluid was supposed to help, but THC can stay in your spit for a long period of time as well (13-15.)

Supposedly, false negatives are the real concern, where intoxication is undetected, but in reality, that is only at the unreasonable THC detection limits of 25ng/ml, officially only valid for 4 hours after use. Low levels of less than 5 ng/mL of THC in saliva will not be detected and neither will it be detected in blood testing (7, 8, 11, 12.), although spit is still valid for initial detection up to 8 hours after cannabis use- as much as a single blood sample or breathalyzer test.

The freedom of cannabis users being jeopardized in the name of public safety, (7, 16,) would be a valid argument only if a means of proper detection was possible (5-7), which illustrates the demand for new oral fluid screening recommendations and equipment to be put in police cruisers.

Lab results aren’t the same as real-world tests

Science-based laws must now be enacted by real-world tests (17,) not laboratory samples (18). Some of these laboratory tests literally used tobacco (19) as a filler for joints with little disclosure over variables in this mixture’s effects. This study is referenced throughout data literature, which legal text uses to establish laws for pure cannabis (7, 16.) Meanwhile, in the shadows, the study was answering drastically different questions.

Another flaw that was pointed out by the same researcher is that cocaine is not a control for cognition (20). Cannabis may instead work together with cocaine at the limbic system, (21, 22, 23) enabling impairment from both. So, testing if cognition after cannabis use does or does not improve after cocaine, is not solely evaluating a function of cannabis tolerance- it’s determining whether an added or synchronous relationship between cocaine and cannabis exists, of which more study is needed.

Currently, wrongful convictions in the name of public safety go beyond necessity. As Britain just changed their laws to eliminate saliva screening (24), it seems this is a trend. They once used THCCOOH, (1) an inactive breakdown product of THC. In minor amounts, it represents cannabis use farther into the past than necessary to control public safety (12), as this remains in the body in various amounts for a long period of time.

Alternatively, ratios between a minute amount of THC and larger amounts of this inactive metabolite can measure recent use in oral screening (10, 13). Typically, cannabis patients and daily users have a small baseline of this metabolite, and it is only seen in larger amounts after a short period of time, up to 12 hours. But baseline THC limits are not the Department of Justice’s concern, (16) even for medicinal users, as they claim chronic use can lead to impairment even weeks after quitting. But this “impairment” is similar to withdrawal symptoms and no worse than the 0.01%-0.03% BAC leeway we have for alcohol (17, 29).

Cannabis’ delayed impairment (26) after intoxication should be compared less severely with a hangover from a night of drinking (27, 28.) At least if actual impairment between the two is so hastily and poorly related through translating standardized lab tests.

Dehydration alone can impair cognition, so does feeling like toxic crap.

But what about hangovers?

Given cannabis detection fails, is alcohol’s hangover skipped for incompetent technology?

Nope, ethyl alcohol metabolites will be detectable in blood the next day after drinking, alongside a cognitive deficit. Of course, this fact is avoided. Whereas emphasis is instead given to THC’s long term impairment, which can be quickly detected days after use with no way to claim you are not impaired. ACMPR licenses are not ‘get out of jail free’ cards either (16.) For the sake of patients, noninvasive roadside testing is a must with a realistic approach to initial detection.

Fears of edibles causing false positives or negatives in oral tests are mute if the following blood test is delayed enough. A similar case happens with alcohol and breathalyzers. But the Draeger still has hopes for its future benefit.

Do not listen to the fear mongering by police. Being able to skip straight to blood tests allows for public safety, but also adds unnecessary jeopardy to those using a legal product responsibly.

Stay tuned for a deep dive into Driving After Cannabis Use, an upcoming work elaborating this current presentation into a full spectrum analysis.


Featured image courtesy of Times of San Diego.


1. Verstraete, Alain; Knoche, A.; Jantos, R.; Skopp, G.; Gjerde, H.; Vindenes, V.; Mørland, J.; et al. (2011). Per se limits: methods of defining cut-off values for zero tolerance. DRUID (Driving under the Influence of Drugs, Alcohol and Medicines).


3. Keeping, Z.; Huggins, R. (2017). Final Report on the Oral Fluid Drug Screening Device Pilot Project. Government of Canada.



6. Canadian Society of Forensic Science; Drugs and Driving Committee (DDC). (2017). Drug Screening Equipment – Oral Fluid Standards and Evaluation Procedures.

7. Canadian Society of Forensic ScienceDrugs and Driving Committee (DDC). (2017). Report on Drug Per Se Limits .

8. Skopp, G.; Pötsch, L. (2008). Cannabinoid concentrations in spot serum samples 24-48 hours after discontinuation of cannabis smoking. PMID: 18334100.

9. Odell M.S.; M.Y. Frei; D. Gerostamoulos; M. Chu; and D.I. Lubman. (2015). Residual Cannabis Levels in Blood, Urine and Oral Fluid Following Heavy Cannabis Use. Forensic Science International. Nature: Scientific Reports. PMID: 25698515.

10. Bosker, W.M.; E.L. Karschner; D. Lee; R.S. Goodwin; J. Hirvonen,; R.B. Innis; E.L. Theunissen, K. P.C Kuypers; M.A. Huestis; and J.G. Ramaekers. (2013). Psychomotor Function in Chronic Daily Cannabis Smokers During Sustained Abstinence. PMID: 23301031.

11. Toennes, S.W., J.G. Ramaekers, E.L. Theunissen, M.R. Moeller, and G.F. Kauert. (2008). Comparison of Cannabinoid Pharmacokinetic Properties in occasional and Heavy Users Smoking a Marijuana or Placebo Joint. Journal of Analytical Toxicology. PMID: 18713514.

12. Karschner EL; Schwilke EW; Lowe RH; Darwin WD; Pope HG; Herning R; Cadet JL; Huestis MA. (2009).Do Delta9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users?. PMID: 19804462.

13. Sebastien Anizan,; Garry Milman; Nathalie Desrosiers; Allan J. Barnes; David A. Gorelick; and Marilyn A. Huestis. (2013). Oral fluid cannabinoid concentrations following controlled smoked cannabis in chronic frequent and occasional smokers. PMID: 23954944.

14. Stefan W. Toennes; Johannes G. Ramaekers; Eef L. Theunissen; Manfred R. Moeller; and Gerold F. Kauert. (2010). Pharmacokinetic Properties of ∆9-Tetrahydrocannabinol in Oral Fluid of Occasional and Chronic Users. Journal of Analytical Toxicology, Vol. 34, May 2010. PMID: 20465868.

15. Dayong Lee; Marilyn A. Huestis. (2014). Current Knowledge on Cannabinoids in Oral Fluid. National Institute on Drug Abuse. PMID: 23983217.

16. Government of Canada: Drug Impaired Driving.

17. CANNABIS USE AND DRIVING: Evidence Review. Canadian Drug Policy Coalition (CDPC). Simon Fraser University. 2017. PDF

18. J.G. Ramaekers; M.R. Moeller; P. van Ruitenbeek; E.L. Theunissen; E. Schneider; G. Kauert. (2006). Cognition and motor control as a function of Delta9-THC concentration. PMID: 16723194.

19. Ramaekers, J.G, J.H. van Wel, D.B. Spronk, S.W. Toennes, K.P.C. Kuypers, E.L. Theunissen, and R.J. Verkes. (2016). Cannabis and Tolerance: Acute Drug Impairment as a Function of Cannabis. PMCID: PMC4881034.

20. Ramaekers JG; van Wel JH; Spronk D; Franke B; Kenis G; Toennes SW; Kuypers KP; Theunissen EL; Stiers P; Verkes RJ .(2016). Cannabis and cocaine decrease cognitive impulse control and functional corticostriatal connectivity in drug users with low activity DBH genotypes. PMID: 26667034.

22. M Solinas, S R Goldberg, and D Piomelli. (2008). The endocannabinoid system in brain reward processes. May; 154(2): 369–383.

23. Cody A. Siciliano; Mark J. Ferris; and Sara R. Jones. (2016).Cocaine self-administration disrupts mesolimbic dopamine circuit function and attenuates dopaminergic responsiveness to cocaine. PMCID: PMC4540675.

24. Gov.UK.: Drugs and Driving: The Law.

25. Health Canada. (2018). Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the cannabinoids.

26. Rebecca L. Hartman; Timothy L. Brown; Gary Milavetz; Andrew Spurgin; Russell S. Pierce; David A. Gorelick; Gary Gaffney; and Marilyn A. Huestis. (2015). Cannabis Effects on Driving Lateral Control With and Without Alcohol. PMCID: PMC4536116.

27. Gunn C, Mackus M, Griffin C, Munafò MR, Adams S. (2018). A systematic review of the next-day effects of heavy alcohol consumption on cognitive performance. PMID: 30144191.

28. Joris C. Verster, Richard Stephens, Renske Penning, Damaris Rohsenow, John McGeary, Dan Levy, Adele McKinney, Frances Finnigan, Thomas M. Piasecki; et al. (2010). The Alcohol Hangover Research Group Consensus Statement on Best Practice in Alcohol Hangover Research. PMID: 20712593.

29. Drugs and Alcohol: Their Relative Crash Risk. EDUARDO ROMANO, Ph.D., PEDRO TORRES-SAAVEDRA, Ph.D., ROBERT B. VOAS, PH.D., JOHN H. LACEY, M.P.H.- 2014 – PMID: 24411797.