Drug Impaired Driving Defence

The Complexity of Drug Impaired Driving Charges

Operating a motor vehicle while your ability to do so is impaired by a drug — whether cannabis, prescription medication, cocaine, methamphetamine, opioids, or any other substance — is a serious criminal offence under Section 320.14(1)(a) of the Criminal Code. The penalties are identical to those for alcohol-impaired driving, including mandatory minimum fines, driving prohibitions, and criminal records.

However, drug impaired driving cases are fundamentally different from alcohol cases in one critical respect: there is no simple, universally accepted equivalent of a breathalyzer for drugs. The prosecution’s case relies on a complex chain of subjective observations, specialized evaluations, and toxicological analysis — each of which presents opportunities for a strong defence.

How the Police Build a Drug Impaired Driving Case

Drug impairment investigations in Ontario follow a specific, multi-step process. At each stage, the police must comply with legal requirements and scientific protocols. A failure at any stage can compromise the entire case.

Stage 1: The Traffic Stop and Initial Observations

The officer who stops your vehicle will note their observations: your driving pattern, the odour of drugs (particularly cannabis), your physical appearance, your speech, your coordination, and any visible drug paraphernalia. These initial observations form the basis for the officer’s suspicion of drug impairment.

We challenge these observations by examining:

• Whether the officer had a lawful basis for the traffic stop
• Whether the observations are consistent with drug impairment or have innocent explanations (fatigue, anxiety, medical conditions, the lingering odour of lawfully consumed cannabis)
• Whether body-worn camera or dashcam footage contradicts the officer’s written notes

Stage 2: Standardized Field Sobriety Test (SFST)

If the officer suspects drug impairment, they may make a demand under Section 320.27(1)(a) for you to perform Standardized Field Sobriety Tests at the roadside. These include:

• Horizontal Gaze Nystagmus (HGN): The officer watches your eyes track a stimulus for involuntary jerking movements.
• Walk and Turn: Walking heel-to-toe along a line and turning.
• One Leg Stand: Balancing on one foot for 30 seconds.

We challenge SFST results on multiple grounds:

• Whether the officer was properly trained and certified to administer the tests
• Whether the tests were administered in proper conditions (level surface, adequate lighting, appropriate footwear)
• Whether the officer correctly applied the standardized scoring criteria — misapplication of the clues is common
• Whether medical conditions, injuries, age, weight, or physical limitations explain the results
• Whether the officer had lawful authority to make the demand — the demand requires a “reasonable suspicion” that you have drugs in your body

Stage 3: Drug Recognition Expert (DRE) Evaluation

If you are deemed to have failed the roadside tests, you are typically arrested and taken to a police station for a 12-step Drug Recognition Evaluation conducted by a Drug Recognition Expert (DRE). This is a specialized protocol that includes:

1. Breath alcohol test (to rule out alcohol as the cause)
2. Interview of the arresting officer
3. Preliminary examination (pulse, pupil size in different lighting)
4. Eye examinations (HGN, Vertical Gaze Nystagmus, Lack of Convergence)
5. Divided attention tests (modified Romberg, walk and turn, one leg stand, finger to nose)
6. Clinical indicators (blood pressure, temperature, pulse at multiple intervals)
7. Examination for muscle tone
8. Examination for injection sites
9. Suspect interview
10. Opinion of the evaluator
11. Toxicological analysis
12. Final opinion

We challenge the DRE evaluation rigorously:

• Was the 12-step protocol followed precisely and in order? Deviations from the protocol undermine the reliability of the opinion.
• Are the clinical observations internally consistent? Different drug categories produce different symptom profiles — if the observations don’t match the drug category the DRE identified, the opinion is unreliable.
• Can the clinical findings be explained by medical conditions, fatigue, stress, anxiety, or prescription medications rather than illicit drug use?
• Was the DRE properly certified and current in their training?
• Did the DRE comply with your Charter rights throughout the evaluation, including your right to counsel?

Stage 4: Blood, Urine, or Oral Fluid Samples

The DRE may demand a sample of blood, oral fluid, or urine for toxicological analysis. We examine:

• Whether the demand was lawfully made — the DRE must have reasonable grounds based on the evaluation
• The chain of custody of the sample from collection to laboratory
• The toxicological results — many drugs and their metabolites can be detected in the body long after any impairing effect has worn off. The presence of a drug in your system does not prove impairment at the time of driving.
• Whether the laboratory followed proper analytical procedures and quality controls

The “Presence vs. Impairment” Problem

This is one of the most significant issues in drug impaired driving law. Unlike alcohol, where a BAC of .08 or above creates a per se offence, drug impairment must be proven based on the totality of the evidence. The mere presence of THC, cocaine metabolites, or other substances in your blood or urine does not prove that you were impaired at the time of driving. THC, in particular, can remain detectable in regular users for days or weeks after the last consumption.

We exploit this distinction aggressively — the Crown must prove impairment, not simply the presence of a substance.

Cannabis-Specific Issues

Since the legalization of cannabis in 2018, drug impaired driving charges involving THC have become increasingly common. The legal framework includes “per se” limits for THC in blood (2-5 nanograms is a summary offence; 5+ nanograms is a hybrid offence), but these limits are controversial and their scientific basis is actively debated. We challenge the reliability and applicability of these thresholds where appropriate.

Why Technical Knowledge Matters

Drug impaired driving law is one of the most rapidly evolving areas of criminal law in Canada. The science behind DRE evaluations, the legal framework for drug testing, and the case law on admissibility are all in flux. We stay at the forefront of these developments, attend specialized training, and consult with toxicologists and forensic scientists to provide the most technically informed defence available.

Related Resources

• DUI & Impaired Driving Defence — alcohol-based impaired driving charges and breath test challenges
• Your Charter Rights in a Criminal Case — how Sections 8, 9, and 10 apply to impaired driving investigations
• Dangerous Driving Defence — sometimes charged alongside or as an alternative to impairment
• What to Do If You’re Pulled Over for a DUI in Barrie — quick-reference guide to your rights at roadside

Charged with drug impaired driving? Contact us for a detailed technical review of your case.