Michael Dyck | Criminal Law

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Is Marijuana Use Impaired Driving?

Michael Dyck

I recently won a very interesting case where Tyler Manaigre admitted to consuming marijuana prior to driving but was acquitted because Provincial Court Judge Devine was not satisfied that his ability to operate a motor vehicle was impaired. Impaired by drug cases are somewhat rare in Manitoba, especially compared to impaired by alcohol cases. You can read the full case here, R. v. Manaigre 2015 MBPC 56.

Very simply put, there is a difference between consumption and impairment whether it is alcohol or drugs. If you have a sip of beer and start driving, we would all agree that you have consumed alcohol but it would be very unlikely that you would be impaired by alcohol at that point. So you can consume without being impaired. However, after you consume a certain amount, you will become impaired.

This case helps outline the legal tests and procedures the police must complete while investigating and charging individuals with driving while impaired by a drug. It is important to keep in mind that you could be charged with driving while impaired even if you are taking a prescription drug as prescribed. In other words, it doesn't matter what sort of drug you are taking if it impairs your ability to drive. It is also important to remember that a level of impairment does not have to be extreme, but a slight degree of impairment of an ability to drive is enough for a judge to convict you of that crime. Finally, a combination of alcohol and drugs can be very problematic if the two interact in a way to combine their effects.

Judge Devine concluded, "In the final analysis, this is a case where the Accused was driving normally, behaving normally and demonstrated no appreciable indicia of marijuana impairment other than possibly some problems during some of the drug evaluation tests."

Judge Devine also commented in her decision, "Although Corporal Sundell testified that sober, able-bodied people do well on the divided-attention tests, I question whether that would be the case for everyone.  Several of the tests sound complicated and very difficult to perform.  I suspect they might well challenge the balance of many completely sober people." In other words, the tests that the police use to determine if someone is impaired or not may have false positives.

Winnipeg Free Press wrote an article about this case "Driving while high not enough for conviction, judge rules." The Winnipeg Sun also wrote an article about this case "High driver acquitted."

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About the author

Michael Dyck is a partner at Rees & Dyck Criminal Defence. He represents clients primarily from Winnipeg, Steinbach, and rural Manitoba. He has extensive experience helping people charged with criminal offences and focuses on building legal strategy with clients. To read more of his articles, please visit his partner's website TomRees.ca.