When THC Levels Don’t Mean Impairment: What R. v. Smith (2025) Tells Us About Cannabis, Driving, and Charter Rights

In November 2025, the Newfoundland and Labrador Provincial Court released a decision that is likely to be cited across Canada in cases involving cannabis and driving: R. v. Smith, 2025 N.J. No. 263.

Why This Case Matters

R. v. Smith is a powerful reminder that:

• Criminal laws must be grounded in evidence

• Charter rights do not disappear at the roadside

• “Per se” limits are not immune from constitutional scrutiny

• Cannabis impairment is not alcohol impairment, and the law must reflect that reality

This decision does not mean cannabis-impaired driving is legal. It means that criminal liability must be tied to real impairment, not guesswork. As more courts confront the science behind THC testing, R. v. Smith will be an important reference point in the ongoing conversation about fairness, evidence, and justice.

At its core, this case asks a simple but important question: Can someone be convicted of a criminal driving offence even if they were not impaired since the Charge is THC in the Blood, Not Impairment?

The Court’s answer on the facts of this case was: No.

Summary of case:

Ms. Smith was charged under section 320.14(1)(c) of the Criminal Code, which makes it an offence to have a blood drug concentration of THC at or above 5 ng/ml within two hours of driving.

This is known as a “per se” offence. Unlike traditional impaired driving charges, the Crown does not need to prove that a person’s driving was actually affected, only that their THC level exceeded the legal limit.

The consequences are serious. A conviction carries:

• A mandatory minimum fine

• A mandatory driving prohibition

• Long-term criminal consequences

• Possible jail time

What Happened at the Roadside?

Ms. Smith was stopped at a police checkpoint on New Year’s Eve.

Police detected an odour of marijuana and required her to provide a saliva sample using approved drug screening equipment. That test registered positive. She was then taken nearly an hour away to a hospital, where police obtained a blood sample.

The result came back months later: 17.1 ng/ml of THC — well above the legal threshold.

But there was a critical problem.

Police observed no signs of impairment. No poor driving. No physical symptoms. No Drug Recognition Evaluation. Nothing to suggest she was actually impaired when she drove.

A Detention That Went Too Far

The Court found that Ms. Smith was arbitrarily detained, in breach of section 9 of the Charter.

From the moment she was stopped until she was released, nearly two hours passed. During that time:

• She was removed from her vehicle without safety concerns

• Held in police cruisers for extended periods

• Transported far from her home

• Left at a hospital on New Year’s Eve with no ride home

The Court described the police conduct as reckless at best, flagrant at worst. This alone raised serious Charter concerns. But the case went much further.

The Bigger Issue: Do THC Limits Actually Measure Impairment?

Ms. Smith challenged the constitutionality of the THC regulation itself, arguing it violated section 7 of the Charter, the right to life, liberty, and security of the person.

To support that challenge, the defence called an expert in pharmacology and cannabis research.

His evidence was clear and uncontroverted:

• THC does not behave like alcohol in the body

• THC can remain detectable long after impairing effects are gone

• Regular users may exceed legal limits days after consumption

• There is no reliable scientific correlation between THC blood levels and driving impairment

• Studies show only about 50% of drivers above the per se limit are actually impaired

Unlike alcohol, there is no predictable timeline a person can follow to know when it is safe, legally, to drive. The Crown did not call its own expert to challenge this evidence.

What the Court Found

The Court held that the THC per se regulation was:

• Overbroad – it captures people who are not impaired

• Vague – it gives no meaningful guidance on how to avoid criminal liability

• Arbitrary – it criminalizes conduct unrelated to actual driving safety

In plain terms, the law punished blameless conduct.

The Court warned that applying the regulation in this way risks turning cannabis use itself which is legal into a criminal offence by another name. As the judge noted, the goal of keeping roads safe is important. But public safety cannot be built on unreliable science or laws that ignore fundamental fairness.

The Result: A Judicial Stay

Because the law prevented Ms. Smith from making full answer and defence — she was not allowed to show she was unimpaired — the Court found her right to a fair trial was compromised. The regulation was not saved under section 1 of the Charter. The charge was stayed.

Disclaimer (Jurisdiction + Not Legal Advice)

This post is for general information only and is not legal advice. R. v. Smith is a decision of the Newfoundland and Labrador Provincial Court. Decisions from another province are not automatically binding on courts in New Brunswick (or elsewhere in Canada). That said, out-of-province cases can still be persuasive, especially where they deal with the same Criminal Code provisions, the same THC “per se” limits, and similar Charter principles. We’re sharing this case because it raises an interesting and potentially important argument about the relationship (or lack of one) between THC blood levels and actual impairment, and because it highlights how courts may scrutinize roadside investigations and the science behind per se offences.