Justice Martin wrote as follows (at paras. 10-11, 13, 16-18, 24-27):

"Under s. 676(1)(a), the Crown can only appeal an acquittal on a “question of law alone”. An appealable error must be traced to a question of law, rather than a question about how to weigh evidence and assess whether it meets the standard of proof (R. v. J.M.H., 2011 SCC 45, [2011] 3 S.C.R. 197, at paras. 25-27; R. v. George, 2017 SCC 38, [2017] 1 S.C.R. 1021, at paras. 15-17). Therefore, the Crown cannot appeal merely because an acquittal is unreasonable (R. v. Biniaris, 2000 SCC 15, [2000] 1 S.C.R. 381, at para. 33).

Errors of law arise, for example, where “the legal effect of findings of fact or of undisputed facts raises a question of law” and where there is “an assessment of the evidence based on a wrong legal principle” (J.M.H., at paras. 28-30). These two types of errors are somewhat similar; they both address errors where the trial judge’s application of the legal principles to the evidence demonstrates an erroneous understanding of the law, either because the trial judge finds all the facts necessary to meet the test but errs in law in its application, or assesses the evidence in a way that otherwise indicates a misapprehension of the law.

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When interpreting a trial judge’s reasons, appellate courts should not parse the reasons of the trial judge in a line by line search for errors. Instead, the reasons are to be “read as a whole, in the context of the evidence, the issues and the arguments at trial, together with ‘an appreciation of the purposes or functions for which they are delivered’” (R. v. Laboucan, 2010 SCC 12, [2010] 1 S.C.R. 397, at para. 16, quoting R. v. R.E.M., 2008 SCC 51, [2008] 3 S.C.R. 3, at para. 16). Appellate courts must attempt to understand the reasoning of the trial judge. However, even if the trial judge articulates the right test, appellate courts may find an error of law if the judge’s reasoning and application demonstrate a failure to properly apprehend the law (George, at para. 16).

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It would not be an error of law if the trial judge simply applied the test in Roy, considered all the circumstances, and came to an unreasonable conclusion regarding whether the accused’s conduct displayed a marked departure from the norm. However, it would be an error of law if the trial judge failed to compare the accused’s actions to what a reasonable person would have foreseen and done in all of the circumstances. This type of error is not a factual matter of weighing evidence, but rather it goes to the legal definition of the mens rea analysis for dangerous driving.

Although the trial judge correctly cited passages from cases which express the applicable legal standards, I find two inter-related errors of law. First, I agree with the Court of Appeal that the trial judge erred by applying a wrong legal principle. Second, and most importantly, I find that the trial judge failed to apply the correct legal test in Roy by not assessing what a reasonable person would have foreseen and done in Mr. Chung’s circumstances.

Applying a wrong legal principle and failing to apply the correct legal test are two sides of the same coin. Both characterizations go to the same essential error of law in this case, which was a failure of the trial judge to properly consider the conduct of the reasonable person in all of the circumstances in determining whether there was a marked departure.

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Although trial judges are not required to set out their analysis in any particular way, the two questions in Roy, at para. 36, are helpful and emphasize the need to compare the accused’s conduct to the conduct of a reasonable person in their circumstances, and by reference to all relevant evidence. This is essential for determining objective mens rea. At some point in the mens rea analysis, the trial judge must work with the facts as found and consider whether, in the totality of the circumstances, a reasonable person would have foreseen the risk and taken the same actions as the accused. Only when there has been an active engagement with the full picture of what occurred can the trial judge determine whether the accused’s conduct was a marked departure from the conduct of a reasonable and prudent driver.

Instead of focussing on what a reasonable person would have foreseen and done in the circumstances, the trial judge engaged in reasoning focussed on the type (speeding) and duration (momentariness) of Mr. Chung’s conduct, to the exclusion of the full picture. His analysis focussed on distinguishing cases where excessive speeding had been found to be a marked departure from the circumstances of this case, rather than examining the risks created by Mr. Chung’s speeding. In other words, he focussed on what Mr. Chung did not do in comparison to these other cases, rather than asking the correct legal question and assessing what risks a reasonable person would foresee arising from Mr. Chung’s momentary speeding in the circumstances.

Had the trial judge turned to consider the circumstances of this case fully and specifically, he would have addressed the fact that Mr. Chung’s conduct did not only include momentary excessive speeding, but also narrowly missing another vehicle turning right in front of him, passing in the curb lane, and accelerating towards a major intersection while aware of at least two vehicles in the intersection. The trial judge found that Mr. Chung was not inattentive while driving, but did not consider how Mr. Chung’s awareness of his surroundings contributed to his conduct being a marked departure from the conduct of a reasonable person. A full analysis in this case would have considered the duration of the speeding, as well as the accused’s control of the car (he switched lanes and then accelerated), the magnitude of speeding (almost three times the speed limit), the location of speeding (approaching a major intersection), and the accused’s awareness of at least two vehicles at the intersection as he approached it. The trial judge then had to consider whether, on these facts as found, a reasonable person would have foreseen the risk of endangering the public by engaging in this conduct and taken steps to avoid it, presumably by not driving so fast.

The duration and nature of the accused’s conduct are only some of the factors to be considered with all of the circumstances in the mens rea analysis. They are not factors that can be taken out of context. It is conceivable that in some contexts, even grossly excessive speed may not establish a marked departure from the standard of care, while in other circumstances speed may not need to be grossly excessive in order to still be a marked departure. Courts must be careful to avoid fettering the analysis in Roy by adopting hard and fast rules regarding when isolated factors will or will not be marked departures. Although case law may be helpful in providing examples of what has previously been determined to be a marked departure, courts must still analyze the accused’s actions relative to the reasonable person in the specific circumstances at issue."

Note: The summary and body are drawn from Eugene Meehan’s SupremeAdvocacy Weekly Updates for the Law Community.