R v Paszczenko; R v Lima – 2010 ONCA 615 (Blair):

[27] “Bolus drinking” is generally meant to describe the consumption of large quantities of alcohol immediately or shortly before driving: see Grosse, at p. 788; R. v. Hall (2007), 83 O.R. (3d) 641 (C.A.), at para. 14. See also Phillips at pp. 158-162, for a description of the “relatively rare” phenomenon, although not by the “no bolus drinking” name.

[28] In establishing that an accused has not engaged in bolus drinking, the Crown is in the unenviable position of having to prove a negative. But how does it meet that onus in circumstances where – as is likely in many cases – it has no statement or evidence from the accused as to his or her drinking pattern at the relevant time and no other witnesses or evidence to shed any light on that issue? That is the dilemma posed, principally, by the Lima appeal.

[29] At one level, the answer is straightforward: the Crown need do very little. The toxicologist’s report is premised – amongst other things – on there being no bolus drinking. In the absence of something on the record to suggest the contrary, on what basis could a trier of fact conclude there was bolus drinking? This Court has answered the question posed by concluding that triers of fact may resort to a common sense inference in such circumstances, namely, that people do not normally ingest large amounts of alcohol just prior to, or while, driving: see Grosse, Hall, and R. v. Bulman, 2007 ONCA 169. As noted above, bolus drinking has been said to be a “relatively rare” phenomenon: Phillips, at pp. 158-162. “No bolus drinking” is therefore largely a matter of common knowledge and common sense about how people behave.
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[32] I would frame the rationale for this approach as the imposition of a practical evidentiary burden on the accused, not to persuade or convince the trier of fact that there was bolus drinking involved, but to point to something in the evidence (either in the Crown’s case, or in evidence led by the defence) that at least puts the possibility that the accused had engaged in bolus drinking in play. The imposition of a practical evidentiary burden to come forward with evidence is simply another way of explaining the invitation to draw a common sense inference which puts the accused in essentially the same spot if he or she cannot point to some evidence to overcome either hurdle.
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[40] Given these facts, together with the application of the common sense inference, the trial judge was entitled to conclude, as she did, that the Crown had proved the facts underlying the toxicologist’s “no bolus drinking” assumption. The SCAJ correctly upheld the finding.