On November 14, 2025, the Supreme Court of Canada (SCC) settled a nationwide debate regarding breath alcohol testing evidence. In its decision, R. v. Rousselle, 2025 SCC 35, a companion case to R. v. Larocque, 2025 SCC 36, the Court confirmed that the Crown is not required to call an analyst to testify or file documents from the analyst in every impaired driving case to prove the reliability of the alcohol standard used in breath testing.
The central question was one of evidence: could the Crown rely solely on the certificate of the qualified technician, a police officer operating the approved instrument, to prove a precondition that the alcohol standard used was certified by an analyst?. The SCC answered a resounding yes.
The Presumption of Accuracy in “80 and Over” Prosecutions
Prosecuting the 80 and over offence hinges on the presumption of accuracy in the Criminal Code. This presumption allows breath test results to be treated as conclusive proof of the accused’s BAC, provided the Crown meets several preconditions beyond a reasonable doubt.
The critical precondition at issue requires proof that, before each breath sample was taken, the qualified technician performed a system calibration check, the result of which was within 10% of the target value of an alcohol standard that is certified by an analyst.
The roles are distinct: the analyst is designated to certify that an alcohol standard is suitable for use. This certification is a guarantee of quality conducted before the standard is shipped. The qualified technician, designated to operate the approved instrument, later performs the calibration check using that standard.
The legal challenge arises because the qualified technician has no direct, personal knowledge of the certification process itself; they only know about the certification via an external document, the analyst’s certificate. Therefore, the technician asserting that the standard was certified is considered hearsay evidence, or even double hearsay if recorded in the technician’s certificate.
Historically, Parliament allowed this evidentiary shortcut, but defence counsel argued the 2018 amendments eliminated this implied exception.
The majority, applying the modern approach to statutory interpretation (text, context, and purpose), concluded that Parliament intended to maintain the scope of the evidence a qualified technician may give.
The overall purpose of the 2018 amendments was to promote coherence, efficiency, simplification, and modernization of the Criminal Code provisions relating to driving offences. The evidentiary scheme was anchored in the alleged scientific consensus regarding the reliability of breathalyzer testes, provided proper procedures were followed. Requiring the Crown to call an additional witness in every case would hinder this simplification objective. Similarly, requiring the Crown to file documents to support this fact in every case was also apparently too complex.
Although the text changed from the former requirement that the standard be suitable for use to certified by an analyst, the meaning did not. Reading the provision in context with the definition of an analyst in the legislation confirmed to the Supreme Court that the two phrases are functionally equivalent.
Standardizing the Framework, Not Raising the Burden
This is because the requirement for certification was relocated to a different subsection in order to resolve a prior statutory anomaly where the requirement varied based on whether the Crown used certificate evidence or testimony from the breathalyzer operator. This relocation was found by the Court to hav been done to standardize and consolidate the precondition for all forms of evidence, rather than increasing the Crown’s burden.
This, in turn, broadened the statutory exception to hearsay. Since asserting that the standard was certified is within the qualified technician’s role of ensuring the calibration was successful, the statement in the technician’s certificate is evidence of the facts admissible in court for its truth, without the need to overcome hearsay rules.
In dismissing the appeal, the majority upheld the historical practice, prioritizing the legislative goal of efficiency and streamlining prosecution while confirming that the technician’s certificate itself holds the necessary evidentiary weight. This interpretation treats the scientific process as a successful sequence of operational checks, allowing the technician to attest to the successful completion of the sequence, rather than requiring the prosecution to prove the separate, foundational facts established by the analyst..
The Dissent’s Warning: Undermining Reliability and Unconstitutionality
Justice Côté, dissenting, argued forcefully that the appeal should have been allowed and an acquittal entered. She stressed that the 2018 amendments were a complete overhaul and introduced new, enhanced safeguards commensurate with the increased strength of the conclusive presumption of accuracy enjoyed by the Crown.
The dissent insisted that Parliament must create exceptions to the presumptive inadmissibility of hearsay very clearly. Allowing the qualified technician to attest to the certification is allowing testimony or hearsay evidence on a matter entirely outside of the qualified technician’s knowledge. This could amount to inadmissible double hearsay for which Parliament did not demonstrate a clear positive intent to create an exception.
Justice Côté warned that the majority’s interpretation likely leads to unconstitutionality. If the Crown relies only on the technician’s certificate, the accused cannot cross-examine the analyst. If the accused cross-examines the technician on the certification process, the technician will be unable to answer, creating a pointless hearsay exception and a quick route to an acquittal once the certificate is impeached.
Why This Case Is Bad For Defence Lawyers and Defendants
The ruling is significantly disadvantageous for the defence in impaired driving prosecutions because it eases the Crown’s burden of proof by maintaining an evidentiary shortcut for foundational scientific evidence.
Allowing the Crown to meet a foundational evidentiary requirement using hearsay that is outside the personal knowledge of the declarant significantly weakens the defence’s ability to challenge that evidence at trial.
The loss of the necessary attendance and cross-examination of the original source of the foundational scientific fact also handcuffs the defence in their ability to challenge the evidence. If the Crown chooses not to file the analyst’s certificate at trial, the accused is precluded from applying to cross-examine the analyst. This hinders the accused’s ability to challenge the underlying accuracy and suitability of the alcohol standard, thereby compromising the accused’s right to make a full answer and defence.
Impeaching the technician is difficult. While the Court notes that disclosure of the analyst’s certificate remains mandatory, allowing the defence to spot defects (like an expired standard) and use this to cross-examine the QT, is a tactical trap. The QT cannot answer questions about the certification process because it is entirely outside of the qualified technician’s knowledge.
This means the defence’s only effective response is to expose the technical weakness of the Crown’s proof, which should not be necessary if the original evidence were properly tendered.
The ruling enables the Crown to benefit from a powerful legal mechanism without rigorous technical proof.
When the Crown successfully proves the preconditions (including certification via the QT’s certificate), the breath test results are regarded as conclusive proof of the accused’s BAC at the time of testing. This standard, which all but guarantees a conviction if unchallenged, requires the Crown to meet the preconditions beyond a reasonable doubt.
In exchange for the increased strength of evidentiary presumptions, Parliament intended to impose more rigorous technical safeguards, such as requiring independent analyst evidence. By finding that the QT’s hearsay evidence is sufficient, the majority permits the Crown to rely on this stronger presumption while sidestepping one of the key safeguards intended to enhance the reliability of the scientific evidence.
For the defence, the Rousselle decision means that a piece of foundational scientific evidence necessary to trigger a conclusive proof presumption can be admitted through a streamlined, hearsay mechanism that severely limits the ability of the defence to challenge the source of that, thereby favouring the efficiency goals of the prosecution getting an easy pathway to a conviction.
