Evidence - Speculation. R v J.C.
In R v. J.C. (Ont CA, 2021) the Court of Appeal canvassed some related (and newly-named) principles of evidence law that relate to judicial notice and speculation:
(1) The Rule Against Ungrounded Common-Sense Assumptions. R v Chanmany
 The first such rule is that judges must avoid speculative reasoning that invokes “common-sense” assumptions that are not grounded in the evidence or appropriately supported by judicial notice: R. v. Roth, 2020 BCCA 240, at para. 65; R. v. Cepic, 2019 ONCA 541, 376 C.C.C. (3d) 286, at paras. 19-27; R. v. Perkins, 2007 ONCA 585, 223 C.C.C. (3d) 289, at paras. 35-36. For clarity, I will call this “the rule against ungrounded common-sense assumptions”.
 To be clear, there is no bar on relying upon common-sense or human experience to identify inferences that arise from the evidence. Were that the case, circumstantial evidence would not be admissible since, by definition, the relevance of circumstantial evidence depends upon using human experience as a bridge between the evidence and the inference drawn.
 Nor is there any absolute bar on using human experience of human behaviour to draw inferences from the evidence. If there was, after-the-fact conduct evidence about things such as flight or the destruction of evidence would not be allowed. Such evidence is relevant because human experience tells us that these behaviours, flight and destroying evidence after a criminal act, are generally undertaken to hide guilt. An absolute bar on using human experience of human behaviour to draw inferences would also mean that evidence that an accused drove a protesting sexual assault complainant to a secluded location could not be used as proof of his intention or her lack of consent. The inferences to be drawn from that evidence depend on common-sense conclusions about what a person acting in a particular manner is likely to be thinking.
 Properly understood, the rule against ungrounded common-sense assumptions does not bar using human experience about human behaviour to interpret evidence. It prohibits judges from using “common-sense” or human experience to introduce new considerations, not arising from evidence, into the decision-making process, including considerations about human behaviour.
(2) The Rule Against Stereotypical Inferences
 The second relevant, overlapping rule is that factual findings, including determinations of credibility, cannot be based on stereotypical inferences about human behaviour. I will call this “the rule against stereotypical inferences”. Pursuant to this rule, it is an error of law to rely on stereotypes or erroneous common-sense assumptions about how a sexual offence complainant is expected to act, to either bolster or compromise their credibility: Roth, at para. 129; R v. A.B.A., 2019 ONCA 124, 145 O.R. (3d) 634, at para. 5; Cepic, at para. 14. It is equally wrong to draw inferences from stereotypes about the way accused persons are expected to act: R. v. Quartey, 2018 ABCA 12, 430 D.L.R. (4th) 381, at para. 21, aff’d 2018 SCC 59,  3 S.C.R. 687; and see Cepic, at para. 24.
 Two points are critical in understanding this rule and ensuring that it does not impede proper judicial reasoning.
 First, like the rule against ungrounded common-sense assumptions, the rule against stereotypical inferences does not bar all inferences relating to behaviour that are based on human experience. It only prohibits inferences that are based on stereotype or “prejudicial generalizations”: R. v. A.R.D., 2017 ABCA 237, 422 D.L.R. (4th) 471, at paras. 6-7, aff’d 2018 SCC 6,  1 S.C.R. 218.
 For example, it is a myth or stereotype that a complainant would avoid their assailant or change their behaviour towards their assailant after being sexually assaulted, and it is an error to employ such reasoning: A.R.D., at paras. 57-58; A.B.A., at paras. 6, 8-10; R. v. Caesar, 2015 NWTCA 4, 588 A.R. 392, at para. 6. Similarly, it is a stereotype that women would not behave in a sexually aggressive manner, or that men would be interested in sex. Reasoning that is based on such inferences is not permitted: Cepic, at paras. 14-16; Quartey, at para. 21.
 By contrast, no stereotype or prejudicial generalization is offended by inferring, where a man drives a resisting woman to a secluded location before touching her sexually, that she did not consent and that he intended to touch her without her consent. Hence, such inferences are appropriate.
 The second critical point in understanding the rule against stereotypical inferences is that this rule prohibits certain inferences from being drawn; it does not prohibit the admission or use of certain kinds of evidence. Professor Lisa Dufraimont makes this point admirably in “Myth, Inference and Evidence in Sexual Assault Trials” (2019) 44:2 Queen’s L. J. 316, at pp. 345-46, 350; and it is reinforced in A.R.D., at paras. 6-8, 62; and Roth, at para. 73.
 For this reason, it is not an error to admit and rely upon evidence that could support an impermissible stereotype, if that evidence otherwise has relevance and is not being used to invoke an impermissible stereotype: Roth, at paras. 130-38. For example, in R. v. Kiss, 2018 ONCA 184, at paras. 101-2, evidence that the complainant did not scream for help was admitted, not to support the impermissible stereotypical inference that her failure to do so undermined the credibility of her claim that she was not consenting, but for the permissible purpose of contradicting her testimony that she had screamed to attract attention.
 By the same token, it is not an error to arrive at a factual conclusion that may logically reflect a stereotype where that factual conclusion is not drawn from a stereotypical inference but is, instead, based on the evidence. For example, although it is a stereotype that men are interested in sex, it was not an error to infer that the accused male was interested in sex at the time of the alleged assault where that inference was based on evidence: Quartey, at para. 21. Similarly, in R. v. F.B.P., 2019 ONCA 157, the trial judge was found not to have erred in finding it implausible that the complainant would consent to spontaneous sex on a balcony, potentially in full view of others, because that inference did not rest in stereotypes about the sexual behaviour of women. The inference was based on evidence about the ongoing sexual disinterest the complainant had shown in the accused, and the ready availability of a private bedroom.
(3) The Effect of Reasoning Errors Related to the Plausibility of Human Behaviour
 Does a reversible error occur whenever a trial judge violates the rule against unfounded common-sense assumptions, or the rule against stereotypical inferences? As a matter of principle, such errors are reversible only when they “ground” the relevant inference by playing a material or important role in the impugned conclusion. Put otherwise, it is not per se a reversible legal error to draw impermissible inferences that do not matter, but it is a reversible legal error to reach a material factual conclusion based on such reasoning.
 Some passages could be taken as limiting the effect of these rules to cases where the impugned factual finding is based solely on impermissible reasoning. For example, the phrase “sole reason” was used by the majority in A.R.D., at para. 31, and, on further appeal, Wagner C.J. described the trial judge as erring by relying “solely” on impermissible stereotypical reasoning: R. v. A.R.J.D., 2018 SCC 6,  1 S.C.R. 18, at para. 2. However, I do not take these decisions as holding that no error will occur so long as additional, permissible lines of reasoning are also offered. In A.R.D., the only reason provided by the trial judge for doubting the complainant’s testimony was the stereotype that she had not altered her behaviour towards the accused after the alleged assault. In my view, when these courts referred to the impermissible stereotypical reasoning as the sole reasoning, they were not defining a precondition to error but were referring to the particular facts of that case. It is instructive that in A.R.D., at paras. 5-6, the majority described the error as “relying on an impermissible stereotype”, or “on prejudicial generalizations” (emphasis added). The majority also quoted, at para. 45, from R. v. R.G.B., 2012 MBCA 5, 275 Man. R. (2d) 119, at para. 59: “A judge would err in law if there is a sound basis to conclude, on appellate review, that a credibility finding was not based on a proper evidentiary foundation, but rather on inappropriate judicial stereotyping” (emphasis added).
 As a matter of principle, an error is “based” on a stereotype or improper inference when that stereotype or improper inference played a material or important role in explaining the impugned conclusion. Where it did so, even if the trial judge offered other reasons for the impugned conclusion, it cannot safely be said that the trial judge would have reached the same conclusion without the error. Where the erroneous reasoning does not play a material or important role in reaching the impugned conclusion, and was only incidental, the accused will not have been prejudiced by it and no reversible error occurs.
 One final point. In argument before us, the Crown emphasized the importance of deferring to credibility determinations made by trial judges. I acknowledge this important practice, but where a trial judge contravenes the rules I have just described, resulting in a material effect on the impugned finding, an error of law has occurred: A.B.A., at paras. 4-5; A.R.D., at para. 28. The error will be reversible, unless the curative proviso in the Criminal Code, R.S.C. 1985, c. C-46, s. 686(1)(b)(iii), is successfully invoked by the Crown.
In R v Chanmany (Ont CA, 2016) the Court of Appeal distinguished speculation from inference:
 First, the distinction between inference and speculation. An inference is a deduction of fact that may logically and reasonably be drawn from another fact or group of facts found or otherwise established at trial. There cannot be an inference without objective facts from which to infer the fact or facts a party seeks to establish. On the other hand, speculation involves theorizing in the absence of evidentiary support. Speculation occurs when a conclusion is reached in the absence of positive, proven, objective facts from which an inference may be drawn.
 Second, without more, judicial speculation, like misapprehension of the evidence, does not mandate appellate correction. The speculation, like a misapprehension, must relate to material parts of the evidence and the error must play an essential part in the reasoning process leading to a finding of guilt: see, for example, R. v. Morrissey (1995), 1995 CanLII 3498 (ON CA), 22 O.R. (3d) 514 (C.A.), at p. 541; R. v. Lohrer, 2004 SCC 80 (CanLII),  3 S.C.R. 732, at paras. 1-2.