R v Stubbs, 2013 ONCA 514 (Watt):

[54] First, as a general (but not unyielding) rule, evidence of misconduct beyond that charged in an indictment, which does no more than portray an accused as a person of (general) bad character, is inadmissible: R. v. Handy, 2002 SCC 56, [2002] 2 S.C.R. 908, at paras. 31 and 36; R. v. Moo, 2009 ONCA 645, 247 C.C.C. (3d) 34, at para. 96; and R. v. Cudjoe, 2009 ONCA 543, 68 C.R. (6th) 86, at para. 63.

[55] Said in a different way, what the law prohibits as a general rule is the introduction of evidence of bad character (as revealed by evidence of other discreditable conduct) for use as circumstantial evidence or proof of conduct on the occasion charged: Handy, at para. 31; Moo, at para. 96. The general exclusionary rule is based on several policy considerations, including the potential for evidence of other discreditable conduct to foster prejudice, to distract the trier of fact from the true focus of the trial, and to waste time: Handy, at para. 37. The prejudice this evidence engenders has been characterized as moral prejudice, the danger that a finding of guilt will be grounded on “bad personhood”, and reasoning prejudice, the danger that the evidence will create confusion or distract a lay trier of fact from its true task: Handy, at paras. 139 – 146.

[56] Second, the general rule excluding evidence of other discreditable conduct is not unyielding. After all, sometimes this evidence is so relevant and cogent that its probative value exceeds its prejudicial effect: Handy, at para. 41; Moo, at para. 97; Cudjoe, at para. 63. To engage the exception to the general exclusionary rule, Crown counsel must establish, on a balance of probabilities, that the probative value of the evidence exceeds its prejudicial effect: Handy, at para. 55.

[57] Third, in prosecutions for domestic homicide, evidence may be admitted of other discreditable conduct of the accused that shows or tends to show the nature of the relationship between the principals, or animus or motive on the part of the accused. This evidence is relevant to prove the identity of the victim or deceased’s killer and the state of mind that accompanied the unlawful killing: Moo, para. 98; Cudjoe, at para. 64. As a threshold requirement, the evidence of other discreditable conduct must be capable of establishing animus or motive: R. v. S. (P.), 2007 ONCA 299, 221 C.C.C. (3d) 45, at paras. 27 and 39; R. v. Johnson, 2010 ONCA 646, 262 C.C.C. (3d) 404, at paras. 97-100. The same principles apply to domestic attempted homicides.

[58] Fourth, when evidence of other discreditable conduct is excluded under the general rule, or admitted by exception, the standard applied on appellate review is deferential: Handy, at para. 153; R. v. B. (C.R.), [1990] 1 S.C.R. 717, at p. 733; and R. v. James (2006), 213 C.C.C. (3d) 235 (Ont. C.A.), at para. 33. Appellate courts will defer to the trial judge’s assessment of where the balance falls between probative value and prejudicial effect unless an appellant can demonstrate that the result of the analysis is unreasonable, or is undermined by a legal error or a misapprehension of material evidence: Handy, at para. 153; James, at para. 33.

[59] Finally, when evidence of other discreditable conduct is admitted because it shows or tends to show animus or motive on the part of an accused, limiting instructions usually required for this evidence are not necessary: Moo, at para. 100; R. v. Jackson (1980), 57 C.C.C. (2d) 154 (Ont. C.A.), at pp. 168-169; R. v. Merz (1999), 46 O.R. (3d) 161 (Ont. C.A.), at para. 59; R. v. Krugel (2000), 143 C.C.C. (3d) 367 (Ont. C.A.), at paras. 85-90; and R. v. Pasqualino, 2008 ONCA 554, 233 C.C.C. (3d) 319, at paras. 65-68.
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[67] It follows, in my view, that evidence of other discreditable conduct of the appellant towards Ms. Steele was relevant to material issues at trial: as evidence of motive or animus to prove the identity of Ms. Steele’s assailant and the state of mind with which the shot was fired. That said, it is necessary to consider the manner in which the evidence was adduced — by filing (and reading into the trial record) a transcript of the guilty plea proceedings — to determine whether the manner of proof tilted the balance in favour of inadmissibility.

[68] In most cases, evidence of other discreditable conduct is introduced through the testimony of those who suffered it (if alive), observed it, or, as admissible hearsay, by those to whom the victim reported it. But there is no closed list of the methods of proof.

[69] Where evidence of other discreditable conduct has been ruled admissible at trial, the substance of the evidence could be incorporated in an agreed statement of facts and filed as a formal admission under s. 655 of the Criminal Code. Indeed, such a practice would reduce the risk associated with the spontaneity and unpredictability of viva voce testimony from witnesses more interested in skewering the accused than obeying judicial constraints.