Updated: August 28, 2026
Legally Reviewed by Alan Pearse
A cannabis-impaired driving arrest in Calgary can put your licence at risk and leave you with a criminal record. Police may issue an immediate Alberta licence suspension or roadside sanction while also laying a criminal impaired-driving charge. A conviction can lead to a further court-ordered driving prohibition.
A charge for driving under the influence of marijuana may disrupt your work, family responsibilities, insurance, and ability to get around the city before the case reaches court.
Alan Pearse focuses his practice exclusively on impaired driving litigation. He has represented thousands of drivers since beginning practice in 2000. He can examine why the police stopped you, what tests they demanded, and whether the evidence supports the charge.
Contact our office now for a free case evaluation.
What Does Cannabis-Impaired Driving Mean in Calgary?
In Calgary, cannabis-impaired driving, often referred to as driving under the influence of marijuana, means operating a vehicle when your ability to drive is compromised to any degree by the drug.
You may also face a separate Criminal Code offence if your blood contains a prohibited concentration of THC within two hours after driving.
How Do Calgary Police Test for Cannabis Impairment?
Calgary police do not use one test in every cannabis-impaired driving investigation. Depending on what an officer observes, the investigation may involve roadside coordination tests, an oral-fluid screening device, a Drug Recognition Evaluation, a blood test, or a combination of these methods.
Standardized Field Sobriety Test
A Standardized Field Sobriety Test is usually conducted at the roadside and looks for physical signs that may indicate impairment. The officer may ask you to complete the horizontal gaze nystagmus test, walk and turn along a straight line, and stand on one leg.
Police can demand these tests when they reasonably suspect that you have a drug in your body and have recently operated a vehicle. Your performance may be used to justify further testing, but it does not measure how much THC is in your system.
Oral-Fluid Sample
A police officer may collect an oral-fluid sample by swabbing the inside of your mouth. Approved roadside equipment tests the sample for the presence of THC and can indicate recent cannabis use. Police may use the result, together with their other observations, to decide whether further testing is necessary.
Drug Recognition Evaluation
A Drug Recognition Evaluation is a structured 12-step assessment conducted by an officer trained as a drug recognition expert. It generally takes place at a police station and may include checks of the following:
- Pulse,
- Blood pressure,
- Body temperature,
- Pupil size,
- Eye movement,
- Coordination, and
- Ability to divide your attention between tasks.
The evaluator may conclude that you are impaired by cannabis, impaired by another category of drug, not impaired, or showing signs of a medical condition. The officer may then demand a bodily sample for laboratory testing.
Blood Test
A blood test measures the concentration of THC in your blood. Police may demand blood samples when they have reasonable grounds to believe that you committed a drug-impaired driving offence or operated a vehicle with a prohibited blood-drug concentration.
The sample must be taken by a qualified medical practitioner or technician who is satisfied that doing so will not endanger your health.
What Are the Consequences of Marijuana Driving Charges in Calgary?
The consequences may come from both the federal criminal process and Alberta’s provincial roadside sanction system.
The Criminal Code sets the following penalties:
- First conviction—minimum $1,000 fine;
- Second conviction—minimum of 30 days in custody; and
- Third or later conviction—minimum of 120 days in custody.
A conviction will also result in a driving prohibition.
Alberta’s Immediate Roadside Sanctions program will create additional consequences before the criminal case is resolved. These will be:
- A driver’s licence suspension,
- A financial penalty,
- Vehicle seizure and towing costs,
- Mandatory remedial education, or
- Participation in an ignition interlock program.
These provincial consequences will begin before the criminal charge is resolved, meaning the effects on your license and daily life will be immediate. Because the criminal case and the Alberta roadside sanction involve different procedures and deadlines, both need to be reviewed carefully.
Alan Pearse can examine the evidence, explain what applies to your case, and help you respond before important deadlines pass.
Can a Cannabis-Impaired Driving Charge Be Defended?
Yes. A cannabis-impaired driving charge may be challenged if the Crown cannot prove impairment, establish a prohibited THC level, or show that police obtained the evidence lawfully.
Alan will examine:
- Justification for the demand. Police need the required legal grounds before demanding roadside testing, a Drug Recognition Evaluation, or a bodily sample.
- Testing procedures. Incorrect instructions, delays, poor testing conditions, or departures from the required procedure may affect the reliability of the results.
- Chain of custody. The timing of collection, storage, continuity, laboratory testing, and disclosure may all become important when the Crown relies on blood or urine evidence.
- Charter rights. The traffic stop, detention, questioning, access to counsel, and testing demands must comply with the Canadian Charter of Rights and Freedoms.
Alan will demand and examine the officer’s notes, police video, testing records, laboratory documents, and the full sequence of events to identify weaknesses in the Crown’s case.
Take the Next Step After a Calgary Cannabis-Impaired Driving Charge
Marijuana driving charges require a defence built around the specific investigation. The case may turn on the officer’s grounds, the roadside procedure, a 12-step DRE, laboratory evidence, provincial deadlines, and the distinction between impairment and a prohibited THC level.
Alan Pearse is the author of A Guide to Breathalyzer Certificates in Canada and regularly lectures lawyers and law students on impaired-driving law. He personally conducts 100% of his trials, so a case accepted by Alan is not transferred to another lawyer for trial.
Contact Alan as soon as possible after a Calgary cannabis-impaired driving arrest or roadside sanction. An early review gives him a better opportunity to document the timeline, obtain evidence, and build a defence of what actually happened.