Medical Marijuana and DUI Charges in Toronto: What to Know

Medical marijuana has been legal in Canada since 2018, but that doesn’t mean patients are exempt from impaired driving laws. In fact, many people with medical authorization face unexpected charges when their use of cannabis intersects with Ontario’s strict DUI rules. A conviction can mean a suspended licence, a criminal record, and lasting damage to your career and reputation.

This guide explains how medical marijuana and impaired driving laws work in Ontario, how THC levels are measured, and what defence strategies can protect your record and your future.

Cannabis and Impaired Driving in Ontario

Under the Cannabis Act and Ontario’s regulations, patients authorized through Health Canada can legally possess and use marijuana for therapeutic purposes. But legalization does not remove the rules around cannabis and DUI charges.

Section 320.14 of the Criminal Code of Canada makes it an offence to operate a vehicle while impaired by drugs — medical or otherwise. As of September 2025, there are no exemptions for medical cannabis users when it comes to impaired driving. If the police can prove your ability to drive was affected by THC, you can be charged.

Zero Tolerance Rules and Medical Exemptions

Ontario has a zero-tolerance policy for certain drivers:

• Novice drivers (G1, G2, M1, M2)
• Drivers under 21 years old
• Commercial drivers (Class A–F licences)
• Road-building and heavy equipment operators

For these groups, any detectable THC through a roadside oral swab can lead to penalties.

Medical cannabis users are exempt from zero tolerance, but that exemption only means trace amounts of THC won’t automatically trigger penalties. If there is evidence of impairment, such as poor driving, failed sobriety tests, or high THC levels on a blood test, charges still apply.

Violations can bring immediate roadside consequences, including:

• Three- to 90-day licence suspensions
• Fines between $350 and $1,000
• Mandatory education or treatment programs

What Counts as Cannabis-Impaired Driving in Ontario

The law defines impairment broadly. Under the Criminal Code, you are impaired if alcohol, cannabis, or any drug affects your ability to drive safely, whether through judgment, coordination, or reaction time.

Cannabis impairment typically lasts three to six hours but can extend longer with edibles, higher doses, or if combined with alcohol. Health Canada warns there is no safe “wait time,” though a six-hour minimum after use is advised.

How Officers of the Law might Judge Cannabis Impairment

Police look for signs such as slurred speech, poor balance, delayed reactions, or erratic driving. Officers may use roadside sobriety tests, oral fluid swabs, and, if warranted, require a blood sample to confirm THC levels.

CBD and Driving in Ontario

CBD itself is non-intoxicating and does not cause impairment. However, many “CBD-dominant” products still contain small amounts of THC. Even trace THC can appear in roadside or blood tests, so medical users should confirm product contents before driving on CBD in Canada.

How Blood THC Levels Are Tested and Used in Court

Cannabis DUI cases in Ontario often hinge on testing:

• Roadside oral swabs detect recent use, with federally approved devices flagging THC around 5–10 ng/ml. These tests only show presence, not impairment.
• Blood tests are the evidential standard in court, though they may be taken hours after a stop, which can distort results.

Criminal thresholds under the Criminal Code include:

1. 2–5 ng/ml THC: summary conviction offence, fine up to $1,000.
2. 5+ ng/ml THC: hybrid offence, minimum $1,000 fine and up to 10 years in jail.
3. 50 mg alcohol + 2.5 ng/ml THC: combined offence, higher mandatory penalties.

Critics argue these numbers don’t reliably reflect impairment, especially for chronic medical marijuana users who may carry baseline THC levels for weeks without feeling impaired. This gap is one of the main challenges in defending against these kinds of DUI charges in Canada.

Penalties for Marijuana-Related DUI in Ontario

The consequences of these driving offences are severe and often immediate:

Provincial (Highway Traffic Act):

• Roadside licence suspensions: 3–90 days
• Vehicle impoundment: 7 days, plus towing/storage fees
• Ignition interlock program: 9 months or more post-conviction
• Mandatory remedial programs costing $500–$1,000

Criminal (Criminal Code):

• Fines ranging from $1,000 to $10,000
• Driving bans of 6–12 months for first offences
• Jail terms up to 10 years for repeat or aggravated offences
• A DUI on your driving record and a criminal record that can affect jobs, immigration, and travel

Insurance:

• Premium increases of 50–200% for 3–6 years
• “High-risk” classification, limiting coverage options

2025 updates:

New amendments to Ontario’s Highway Traffic Act make impaired driving charges in 2025 even stricter:

• Lifetime driving bans for fatal impaired offences (with limited reinstatement after 10 years and ignition interlock)
• Mandatory interlock for all convictions, no exceptions
• Electronic monitoring for repeat offenders

Unique Challenges for Medical Cannabis Patients

Medical cannabis patients face a different set of risks:

1. Baseline THC levels: Regular users often test between 2–50 ng/ml, even if they haven’t consumed for days.
2. False positives: Roadside saliva devices cannot differentiate between therapeutic use and impairment.
3. Strain differences: CBD-dominant strains are less impairing, but tests don’t show strain or dosage.

This creates situations where a patient can face charges despite following medical advice and not actually being impaired.

Defending Against Medical Marijuana DUI Charges

Successfully defending against medical marijuana DUI cases requires a comprehensive understanding of both legal procedure and scientific evidence. Common strategies include:

• Challenging the stop or detention: Was there reasonable suspicion to demand a roadside swab?
• Questioning device accuracy: Oral fluid devices are only 70–90% reliable; calibration and maintenance issues are common.
• Scrutinizing blood tests: Delayed sampling, chain-of-custody errors, or lab mistakes can undermine results.
• Highlighting a lack of impairment evidence: Normal field sobriety performance, absence of erratic driving, or no accident can weaken the Crown’s case.
• Medical-specific arguments: Presenting Health Canada authorization, expert testimony on non-impairing doses, or evidence of CBD-heavy treatment plans.

Cannabis DUI cases can end with dismissals or reductions, often because of procedural flaws. In many cases, an experienced criminal lawyer can negotiate reduced penalties, secure diversion programs, or have charges dismissed.

Choose Posner Craig Stein to Defend Against Your Medical Marijuana DUI Charges

The lawyers at Posner Craig Stein bring decades of combined experience and have defended thousands of cases at every level of court, from trial to appeal. That depth of practice means we know how to challenge the science behind THC testing, expose weaknesses in drug recognition evaluations, and pursue Charter applications where police have overstepped.

Facing a cannabis-related DUI charge is stressful and often confusing, particularly for medical marijuana patients. We take the time to explain each step, provide clear advice, and build a strategy that protects your interests.

Protect Your Record and Your Future

A cannabis-related DUI can put your licence, your livelihood, and your reputation at risk, even if you are authorized to use medical marijuana. You don’t have to face these charges alone.

Posner Craig Stein has the courtroom experience, strategic insight, and client-first approach to defend you when the stakes are highest. Contact us for a confidential consultation and put a recognized team of criminal defence lawyers on your side.