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The Supreme Court of Canada’s (“SCC”) decision in R v Larocque, 2025 SCC 36 [Larocque] addresses the scope of the evidentiary shortcuts available to the Crown in impaired driving prosecutions. Specifically, the SCC clarified what must be proven before the statutory presumption that breath test results are accurate can apply and whether the “target value” used in machine calibration forms part of that requirement.
Facts
On August 16, 2019, Mr. Larocque was stopped at a Royal Canadian Mounted Police (“RCMP”) sobriety checkpoint in New Brunswick. The officer formed reasonable grounds that he had operated a vehicle while impaired, arrested him, and brought him to the station for breath testing. Mr. Larocque provided two breath samples registering 110 mg and 120 mg of alcohol per 100 mL of blood. He was charged with the “80 and over” offence under s. 320.14(1)(b) of the Criminal Code, RSC 1985, c C-46 [Code], for having a blood alcohol concentration at or above 80 mg within two hours of driving (Larocque, para 5).
At trial, the Crown called the arresting officer, the qualified technician, and an additional officer who had served copies of the two certificates of two analysists on Mr. Larocque. The crown also filed the qualified technician’s certificate and two analysts’ certificates (Larocque, para 6).
Judicial history
New Brunswick Provincial Court
The trial judge convicted Mr. Larocque of the “80 and over” offence, holding that the Crown could rely on the presumption of accuracy because the preconditions in s. 320.31(1)(a) were satisfied (Larocque, paras 9–11). She declined to follow Alberta authority requiring different proof and instead followed appellate decisions holding that certification of the alcohol standard could be proven through either the qualified technician or an analyst. She found the presumption of accuracy available even if the analysts’ certificates were inadmissible, and in any event concluded those certificates were admissible (Larocque, para 10). She did not address whether the Crown had to prove the target value itself.
New Brunswick Court of King’s Bench
On summary conviction appeal, the conviction was upheld (Larocque, paras 12–14). The appeal judge considered conflicting appellate jurisprudence and agreed with the reasoning that the certificate of the qualified technician could establish the preconditions to the presumption of accuracy (Larocque, para 13). The trial judge was held to have not erred in law and dismissed the appeal (Larocque, para 14). The issue of proving the target value, however, was not explicitly addressed.
New Brunswick Court of Appeal
The New Brunswick Court of Appeal dismissed the further appeal (Larocque, paras 15–17). It held that the Crown could rely on the presumption of accuracy based on the qualified technician’s certificate, which stated that the calibration result was within 10 percent of the target value of a certified alcohol standard Since the technician must know that value to conduct the check, the certificate was deemed sufficient proof (Larocque, para 16). The judge also held that disclosure provisions did not require the Crown to disclose information about the target value (Larocque, para 17).
Issue and Background
Does s. 320.31(1)(a) of the Code require the Crown to prove the target value of the alcohol standard used for the system calibration check in order to rely on the presumption that breath results are accurate (Larocque, paras 8, 15)?
For context, impaired driving prosecutions under the modern Code framework operate through a structured, science-based evidentiary scheme. Parliament’s 2018 reforms were designed to simplify and streamline “80 and over” prosecutions and reduce technical litigation (Larocque, para 34). Rather than requiring the Crown to repeatedly prove the scientific reliability of breath-testing instruments, the legislation builds reliability into standardized procedures that must be followed (Larocque, para 37).
The centre of this framework is the presumption of accuracy. When the statutory preconditions are met, breath test results are treated as conclusive proof of a person’s blood alcohol concentration at the time of testing (Larocque, paras 38, 41). This significantly narrows the issues at trial. The focus shifts from general scientific debate to whether the required statutory steps were properly carried out.
Those steps include two key safeguards that a qualified technician must perform before breath samples are taken. A system blank test ensures the instrument reads zero when no alcohol is present. A system calibration check verifies that the instrument produces a result within an acceptable range of a known alcohol concentration (Larocque, para 37). These procedures are the mechanism through which Parliament ensures the instrument is functioning properly in the individual case.
Disclosure obligations also play a role in this structure. The Crown must provide information that allows the accused to assess whether these preconditions were satisfied and to challenge them if necessary (Larocque, paras 24–27). Larocque arises directly from this framework. The dispute concerns how strictly courts must interpret and enforce these procedural safeguards before allowing the presumption of accuracy to determine the outcome.
Decision
Majority
The appeal was dismissed with the conviction affirmed (Larocque, paras 42–43). Rowe and Moreau JJ., writing for the majority, held the Crown must disclose the target value under s. 320.34(1)(b), as it is necessary to understand the results of the system calibration check (Larocque, paras 24–28). However, the Crown is not required to prove the target value at trial to rely on the presumption of accuracy (Larocque, paras 33–39).
Parliament made the precondition the fact that the qualified technician conducted a calibration check and obtained a result within 10 percent of the target value, not proof of the numerical target value itself (Larocque, paras 33, 37–38).
Dissent (Côté J.)
Dissenting, Côté J. agreed the target value must be disclosed, but would also require the Crown to prove it when invoking a presumption that makes conviction nearly inevitable (Larocque, paras 45–46, 61, 66). In her view, without proof of the comparator, including any corrected target value, compliance with s. 320.31(1)(a) is incomplete (Larocque, paras 63–66, 70). She would allow the appeal and enter an acquittal (Larocque, paras 72–73).
Analysis
At first glance, this case appears highly technical; a dispute over whether the Crown must prove a numerical target used during machine calibration. Fundamentally, though, the case is not about numbers. Rather, it is about how far Parliament can go in simplifying impaired driving prosecutions without hollowing out the accused’s procedural protections.
The Presumption of Accuracy Is Doing the Heavy Lifting
Under the modern impaired driving scheme, once the Crown satisfies the preconditions in s. 320.31(1), breath test results serve as conclusive proof of a person’s blood alcohol concentration. That is an extraordinary evidentiary shortcut, replacing what used to be a trial about scientific reliability with a largely paperwork-driven process.
The majority accepts that this shortcut is constitutionally tolerable because it rests on standardized scientific procedures. The system blank test and system calibration check are not formalities. They are the safeguards meant to ensure the machine is functioning properly before it produces the evidence that will effectively decide the case (Larocque, paras 37–38).What the Court does here is define how strict those safeguards must be in court.
The Majority Draws a Line Between Disclosure and Proof
The Court separates what the accused must be told from what the Crown must prove. The majority holds that the target value must be disclosed because, without it, the accused cannot understand whether the calibration result fell within the permitted 10 percent range (Larocque, paras 26–28). Disclosure allows the defence to test whether the statutory preconditions were met.
However, the Court refuses to elevate that same information into an evidentiary requirement at trial. For the majority, Parliament’s goal in the 2018 reforms was to streamline “80 and over” prosecutions, not recreate technical litigation over scientific minutiae (Larocque, para 34). Requiring proof of the target value would convert a procedural safeguard into a new technical hurdle. The key shift is that accuracy is ensured by the procedure being followed, not by relitigating the underlying numbers in every trial.
The Dissent Sees This as a Rights Problem
Côté J sees the target value as the comparator that makes calibration meaningful (Larocque, paras 63–66). Without proof of that comparator, the Crown is asking the court to accept that the machine worked while relying on a presumption that makes conviction nearly inevitable (Larocque, para 45).
Her concern is institutional. Once the presumption operates, the trial’s truth-seeking role shrinks dramatically. That makes strict compliance with each precondition essential to maintaining the presumption of innocence. Treating the target value as something that must be disclosed but not proven risks turning the Crown’s burden into a paper formality (Larocque, para 66).
What this Means Going Forward
Larocque confirms that impaired-driving trials are increasingly compliance hearings rather than scientific contests. Defence leverage now lies primarily in disclosure and in the ability to cross-examine the qualified technician where the records suggest irregularities. The majority prioritizes systemic efficiency and deference to standardized science; the dissent insists on trial-level verification as the price of a near-conclusive presumption.
Ultimately, the decision shows that the Court is prepared to allow Parliament to tilt decisively toward efficiency, so long as the defence retains enough information to meaningfully challenge whether the statutory steps were actually followed. Whether that balance adequately protects the accused, or merely preserves the appearance of protection, is the unresolved tension at the heart of Larocque.