This Week at the SCC: Breathalyzer Accuracy

Editor’s Note: This post was written as a preview of an upcoming Supreme Court of Canada decision for the Fantasy Courts website and newsletter. Photo by Samuele Errico Piccarini on Unsplash

😮‍💨 On Friday, November 14, 2025, the Supreme Court of Canada will release its decisions in R. v. Rousselle and R. v. Larocque. Both appeals, from New Brunswick, raise the same question: how much proof does the Crown need to rely on the presumption of accuracy for breathalyzer results under section 320.31(1)(a) of the Criminal Code?

📃 On November 7, 2025, the Supreme Court of Canada released its decision in R. v. Rioux, 2025 SCC 34, about how courts should assess evidence of a person’s capacity to consent to sexual activity. In a 5:4 split, the Court ruled that when a person cannot remember what happened during a sexual act, a judge must look at all the surrounding evidence, including direct and circumstantial evidence, not just what the person can recall in their testimony. It upheld the Court of Appeal’s decision to order a new trial.

🎯 Only 11% of Fantasy Courts players correctly predicted the result.

🔮 Head over to Fantasy Courts to lock in your predictions for this week’s decisions, or read more about the cases below. A recap of the last decision predicted follows.

Case to Predict: How Much Proof is Needed for Breathalyzer Accuracy?

Appeal by leave from Rousselle v. R., 2024 NBCA 3 and Larocque v. R., 2024 NBCA 4

📄 SCC factums (1 and 2) and webcast 🎥

What Happened?

Both the appellants were stopped by police and charged with operating a vehicle with a blood-alcohol concentration over the legal limit. Their breath tests were conducted on an approved instrument (the Intox EC/IR II). The issue is whether the Crown proved that the alcohol standard used to calibrate the machine was properly certified by an analyst — a legal prerequisite for the test results to be accepted as conclusive proof of intoxication.

At trial, the courts reached different outcomes: Mr. Rousselle was originally acquitted, while Mr. Larocque was convicted. A summary conviction appeal was allowed with respect to Mr. Rousselle, resulting in a conviction being entered. The New Brunswick Court of Appeal upheld both convictions, following reasoning from the Yukon’s R. v. MacDonald decision that allows the Crown to rely on a police technician’s certificate without separate proof from an analyst.

What Was Argued at the SCC?

Appellants: They argue that Parliament’s 2018 changes to the impaired-driving provisions were meant to add safeguards, not remove them. They say the Crown must present direct evidence from an analyst, either by certificate or testimony, to prove that the calibration standard was certified and valid. Otherwise, the breath test results rest on inadmissible hearsay from the technician.

Respondent: The Crown maintains that Parliament intended to simplify these trials, not complicate them. As long as the technician’s certificate or testimony tracks the exact statutory language — that the calibration check was within 10% of the target value of a certified standard — the presumption of accuracy should apply. Requiring analysts to testify in every case would undo Parliament’s goal of efficiency.

What Else Should You Know Before Making a Prediction?

The Court will have to decide whether the Crown can prove that the breathalyzer was working properly through the technician’s certificate alone or must produce independent proof from an analyst about the calibration standard’s certification and target value. The outcome will settle a national divide: Alberta’s R. v. Goldson demanded direct analyst proof, while Yukon’s R. v. MacDonald and New Brunswick’s rulings said the technician’s word is enough. I’m leaning towards the Alberta approach being adopted and the appeals being allowed. Like the last three appeals, I’m expecting another close split.

Previous Case Recap: Rioux

R. v. Rioux, 2025 SCC 34
Held (5:4): Appeal dismissed and Court of Appeal’s order for a new trial upheld. If the complainant has no recall of the sexual activity in question, the trier of fact is obliged to consider all credible and reliable circumstantial evidence.

Key points:

• To have capacity to consent, a person must be capable of understanding: the physical act and its sexual nature, the sexual partner’s identity, and the fact that the person can refuse to participate.
• A person who experiences memory loss can still provide relevant evidence about their lack of consent, or their incapacity to consent.
• The judge must look at all the surrounding evidence, including direct and circumstantial evidence, not just what the person can recall in their testimony.
• The trial judge erred by saying that direct evidence about a person’s state of mind is a requirement for determining their incapacity and absence of consent. The trial judge also failed to understand that the complainant’s circumstantial evidence was legally relevant, independent of any direct evidence.
• The dissent would have restored the acquittals on the basis that the trial judge neither erred in applying the legal principles relating to sexual assault nor failed to consider all of the evidence.

📊 Another tough one. Only 11% of Fantasy Courts players predicted correctly.

Thanks for reading and playing Fantasy Courts. If you liked today’s newsletter, we’d love for you to share it with a friend, or you can sign up to receive it as an email: https://mailchi.mp/37b20ffd0198/fantasycourts

-Tom Slade