***Mise à jour importante ici.
La Cour d’appel de l’Ontario reprend en 10 étapes les principes gouvernant l’admissibilité d’une preuve d’un comportement post-infractionnel. Elle distingue entre autre les cas où la preuve est utilisée purement à titre narratif, aux cas où la preuve est directement utilisée pour prouver la culpabilité de l’accusé :
 The principles governing the admissibility and jury use of evidence of post-offence conduct are well established and not in need of lengthy recital. That said, the precedents elucidate several principles of importance in the assessment of this ground of appeal.
 To begin, evidence of post-offence conduct is circumstantial evidence which invokes retrospective reasoning to link something said or done later to the speaker’s or doer’s participation in a prior event which constitutes the actus reus of an offence with which she or he is charged: R. v. White, 2011 SCC 13 (CanLII),  1 S.C.R. 433, at paras. 17, 105; R. v. B. (P.), 2015 ONCA 738(CanLII), 127 O.R. (3d) 721, at para. 165.
 Second, the bulk of evidence of post-offence conduct enters the trial record as an unremarkable part of the narrative of relevant events: White, at paras. 140 and 157; R. v. Cornelius, 2011 ONCA 551 (CanLII), 283 O.A.C. 66, at para. 19. Where evidence of post-offence conduct is received as pure narrative, no special or limiting instruction about its use is required: White, at para. 47.
 Third, as a general rule, evidence of post-offence conduct is not subject to special admissibility rules. Nor does it require that a trial judge caution the jury about its use in proof of guilt: White, at paras. 105, 137; Cornelius, at para. 19; R. v. Rosen, 2018 ONCA 246 (CanLII), 361 C.C.C. (3d) 79, at para. 50.
 Fourth, the influence of evidence of post-offence conduct in the determination of an accused’s guilt is a variable, not a constant.
 Sometimes, the Crown will tender evidence of post-offence conduct as an essential component of its case. When this is so, it is for the Crown to satisfy the trial judge, as with any item of evidence, that the evidence is relevant and admissible. To meet the modest threshold for relevance, the Crown must establish that the evidence of post-offence conduct, as a matter of logic, common sense and human experience, has a tendency to help the jury resolve a live factual issue in the trial: White, at paras. 36, 140, 169. To meet the admissibility requirement the Crown must show that no exclusionary rule bars reception of the evidence.
 In other cases, evidence of post-offence conduct will be admitted as narrative only and not enlisted as an essential component in proof of guilt.
 Fifth, where evidence of post-offence conduct is put forward as an integral element in the Crown’s attempt to establish guilt, it is ultimately for the jury to decide, on the basis of the evidence as a whole, whether the evidence of post-offence conduct relates to the offence charged rather than to something else and, if so, how much weight, if any, the evidence should be accorded in the final determination of guilt or innocence: White, at para. 137; Cornelius, at para. 19.
 Sixth, as a general rule, evidence of post-offence conduct may be relevant to and admissible to assist in proof of an accused’s culpability in an offence, but not on the level of that culpability: R. v. Czibulka, 2011 ONCA 82 (CanLII), 267 C.C.C. (3d) 276, at para. 55; R. v. Stiers, 2010 ONCA 382 (CanLII), 255 C.C.C. (3d) 99, at para. 55, leave to appeal refused,  S.C.C.A. No. 150. But this rule is not unyielding. After all, relevance is a relative concept. The relevance of evidence of post-offence conduct depends upon myriad factors such as:
- the nature of the conduct;
- the facts sought to be inferred from it;
iii. the positions of the parties; and
- the totality of the evidence.
No prefabricated rule determines the relevance or lack of relevance of evidence of post-offence conduct to a particular fact in issue: Stiers, at para. 56.
 Seventh, experience teaches that in some cases jurors may attach more weight to evidence of post-offence conduct than is warranted. In such cases, it makes sense for judges to alert jurors to the accumulated learning of the courts about the evidence, all the more so when that learning may be counter-intuitive for at least some jurors: Cornelius, at para. 19; White, at para. 138.
 Eighth, consistent with general principle, where evidence of post-offence conduct is admissible for one purpose but not another, as a general rule, a trial judge should expressly instruct the jury on the permitted and prohibited use(s) of this evidence. But failure to do so in express terms is not always fatal: Cornelius, at para. 24; Czibulka, at paras. 60-61; Stiers, at paras. 61-62; R. v. Huard, 2013 ONCA 650 (CanLII), 302 C.C.C. (3d) 469, at para. 83, leave to appeal refused,  S.C.C.A. No. 13.
 Two further points will round out this discussion of governing principles.
 Where the evidence of post-offence conduct consists of or includes advancement of an alibi, we distinguish the evidentiary value of a disbelieved alibi from that of an alibi that has been fabricated or concocted. A disbelieved alibi is an evidentiary naught. On the other hand, an alibi that independent evidence establishes as concocted or fabricated at the instance of an accused may support an inference of guilt, but is not conclusive evidence of guilt: R. v. Hibbert, 2002 SCC 39 (CanLII),  2 S.C.R. 445, at para. 67; R. v. Nedelcu, 2012 SCC 59 (CanLII),  3 S.C.R. 311, at para. 23; R. v. Cyr, 2012 ONCA 919 (CanLII), 294 C.C.C. (3d) 421, at para. 75.
 Finally, a general instruction that jurors might consider an accused’s “words and actions before, at the time, and after” the conduct that constitutes the actus reus of an offence in determining the accused’s state of mind is simply a general guideline that encourages jurors to consider an accused’s actions in their totality. As such, it is not an instruction to infer an accused’s state of mind merely from conduct after the incident: R. v. Jaw, 2009 SCC 42 (CanLII),  3 S.C.R. 26, at para. 25.