Character Evidence. R. v. G.M.C.
In R. v. G.M.C. (Ont CA, 2021) the Court of Appeal set out when evidence of bad character was relevant for assessing credibility:
 The limits on the use of bad character evidence were set out in R. v. Calnen, 2019 SCC 6,  1 S.C.R. 301, at para. 64:. R. v. Camara
As the majority of the Court of Appeal noted, the evidence of Mr. Calnen's after-the-fact conduct was admissible on the question of his credibility. Evidence of extrinsic discreditable conduct that is otherwise relevant and admissible with respect to an issue in the case may be used to assess the accused's overall credibility. In R. v. G. (S.G.), 1997 CanLII 311 (SCC),  2 S.C.R. 716, at para. 70, Cory J. laid to rest any doubt about this common sense proposition:
To require a jury to compartmentalize its thinking even further than this would be artificial and unnecessarily convoluted. It is a matter of common sense that evidence of bad character may reflect badly on the accused's credibility, and that the jury can use it as a factor in determining if the accused is likely to be telling the truth. This is not the same thing as suggesting that the accused is guilty because she is a bad person, or may have a disposition to commit the type of crime for which she is charged.
In R. v. Camara (Ont CA, 2021) the Court of Appeal (Watt JA) comments on bad character evidence:
 It is uncontroversial that, generally, the Crown is not permitted to use bad character evidence as circumstantial proof of conduct. We insist that, if guilt is to be established, it be by proof of conduct, not proof of character: R. v. Moo, 2009 ONCA 645, 247 C.C.C. (3d) 34, at para. 96, leave to appeal refused  S.C.C.A. No. 152; R. v. Handy, 2002 SCC 56,  2 S.C.R. 908, at para. 31; R. v. G. (S.G.), 1997 CanLII 311 (SCC),  2 S.C.R. 716, at para. 63.. R. v. Norris
 However, the character rule is subject to exceptions. Among those is where evidence revealing an accused’s bad character is relevant to an issue in the case, provided the probative value of the evidence on that issue exceeds its prejudicial effect: Moo, at para. 97; Handy, at para. 41; G. (S.G.), at para. 65.
 The categories of relevance are not closed. Relevance is relative and is assessed in the context of the case as a whole and the positions of counsel. Evidence of bad character may be exceptionally admitted where relevant to establish motive or animus, state of mind (such as fear on the part of a victim), narrative, or to provide context for other events: R. v. T. (J.A.), 2012 ONCA 177, 288 C.C.C. (3d) 1, at para. 54; R. v. Walker (1994), 1994 CanLII 8725 (ON CA), 90 C.C.C. (3d) 144 (Ont. C.A.), at pp. 152-3; R. v. MacDonald (2002), 2002 CanLII 14251 (ON CA), 170 C.C.C. (3d) 46 (Ont. C.A.), at para. 35.
 A judge presiding in a criminal jury trial has a duty to ensure that only relevant, material, and admissible evidence is received: T. (J.A.), at paras. 50, 92. Where evidence of limited relevance or admissibility is received, the judge has an obligation to instruct jurors about the permitted and prohibited use of that evidence: R. v. Calnen, 2019 SCC 6,  1 S.C.R. 301, at para. 113 per Martin J., (dissenting, but not on this point); R. v. Ball, 2019 BCCA 32, 371 C.C.C. (3d) 381, at para. 91; T. (J.A.), at para. 50.
In R. v. Norris (Ont CA, 2020) the Court of Appeal comments on similar fact evidence as a form of bad character evidence:
 The presumptive inadmissibility of similar act evidence – a form of bad character evidence – is rooted in concerns over moral and reasoning prejudice. Moral prejudice results where triers of fact decide cases, not based on what the accused has done, but based on the kind of person the trier of fact perceives the accused to be: Handy, at paras. 31, 36; R. v. Lo, 2020 ONCA 622, at para. 110. Reasoning prejudice results where similar act evidence gives rise to confusion and distracts the trier of fact from its proper focus on the charges before the court. . R. v. Cook
In R. v. Cook (Ont CA, 2020) the Court of Appeal considers when 'bad character' evidence is admissible:
 In his leading judgment in R. v. Handy, 2002 SCC 56,  2 S.C.R. 908, Binnie J. said, at para. 72: “Discreditable disposition or character evidence, at large, creates nothing but ‘moral prejudice’ and the Crown is not entitled to ease its burden by stigmatizing the accused as a bad person.” See also R. v. Calnen, 2019 SCC 6,  1 S.C.R. 301, at para. 44, per Moldaver J. This is precisely what happened in this case – the Crown attempted to ease its burden by supplementing what appeared to be a formidable case with irrelevant and gratuitous bad character evidence.. R v Bos
 Evidence of gang association, affiliation, or membership is bad character evidence. It is presumptively inadmissible: R. v. Phan, 2020 ONCA 298, 387 C.C.C. (3d) 383, at para. 90. It impels the prohibited inference that the accused is the type of person who is likely to have committed the offence. This type of evidence is particularly dangerous because it involves “unrelated criminal activity”: R. v. Riley, 2017 ONCA 650, 137 O.R. (3d) 1, at para. 21. More generally, it may also insinuate that the accused embraces a positive attitude towards the criminal lifestyle.
 Although evidence of gang affiliation is presumptively inadmissible, it has a legitimate place in some trials. As Strathy C.J.O. explained in Phan, at para. 91:
While evidence of gang membership can be highly prejudicial, it may be relevant for a variety of purposes. Like all bad character evidence, it may be admissible on an exceptional basis where its probative value outweighs its prejudicial effect. It may be admissible to provide context or narrative, to establish animus or motive, or to establish the accused's state of mind or intention, among other purposes. The case law is replete with the admission of gang association evidence for these and other purposes. [Emphasis added.] In any given case, it is incumbent on the trial judge to determine whether and to what extent such evidence is admissible. This is required by the trial judge’s overarching duty as a gatekeeper: R. v. Grant, 2015 SCC 9,  1 S.C.R. 475, at para. 44. As Cronk J.A. wrote in R. v. B.D., 2016 ONCA 673, 342 C.C.C. (3d) 217, at para. 51, “[i]t was incumbent on the trial judge to ensure that only relevant and material evidence was placed before the jury and that the probative value of such evidence outweighed its prejudicial effect.”
 The Hells Angels evidence should never have been admitted at this trial. It was not relevant to any of the issues the jury was required to decide: (1) whether the appellant possessed the steroids for the purpose of trafficking; (2) whether the appellant was in possession of the cocaine that was seized behind his backyard; and (3) whether the cash seized from the appellant’s and his father’s residences was derived from the commission of crime (i.e., the drug offences).
In R. v. Bos (Ont CA, 2016) the Court of Appeal sets out the basic approach of the court to the admission of character evidence, here referred to in it's negative form as 'discreditable conduct' evidence:
 Evidence is discreditable when it tends to show conduct of the accused, which would be viewed with disapproval by a reasonable person, beyond what is alleged in the indictment: see e.g. R. v. Johnson, 2010 ONCA 646 (CanLII), at para. 90.
 Such evidence is presumptively inadmissible because “[i]ts potential for prejudice, distraction and time consumption is very great and these disadvantages will almost always outweigh its probative value”: R. v. Handy, 2002 SCC 56 (CanLII),  2 S.C.R. 908, at para. 37.
 In Johnson, at paras. 97-101, Rouleau J.A. discussed the jurisprudence on discreditable conduct evidence adduced to support motive. He explained that such motive evidence is not automatically admissible. Rather, the trial judge must satisfy herself or himself that the probative value of the evidence outweighs its prejudicial effect. He noted that discreditable conduct evidence that is adduced to advance a speculative theory of motive ought to be excluded. However, “evidence that provides the trier of fact with real insight into the background and relationship between the accused and the victim, and which genuinely helps to establish a bona fide theory of motive is highly probative”, and thus more likely to outweigh its inherent prejudicial effect: Johnson, at para. 101.