Criminal - Pollock Applications. R. v. Davani
In R. v. Davani (Ont CA, 2023) the Court of Appeal considered Pollock applications, where "in a joint trial, co-accused parties may, in their own defence, introduce evidence that could not be tendered as part of the crown’s case, including relevant evidence that demonstrates the disposition or propensity of a co-accused to commit the offence charged":
 In Pollock, this court held that, in a joint trial, co-accused parties may, in their own defence, introduce evidence that could not be tendered as part of the crown’s case, including relevant evidence that demonstrates the disposition or propensity of a co-accused to commit the offence charged. Before such evidence is admissible, “[t]here must be some evidentiary foundation to support this assertion” of relevance: Pollock, at para. 106. There is discretion to exclude relevant defence evidence, even where an evidentiary foundation exists, but given the necessity of permitting accused pesons to present full answer and defence, unlike Crown evidence that can be excluded where its probative value is outweighed by its prejudicial effect, evidence relevant to a defence is admissible unless its prejudicial effect substantially outweighs its probative value: Pollock, at para. 110. I will elaborate.
 In R. v. J.A.T., 2012 ONCA 177, 288 C.C.C. (3d) 1, at para. 52, Watt J.A., writing for this court, identified the different ways in which the “inherent prejudicial effect of evidence of bad character can infect a jury’s deliberative process”: 1) the jury may assume the accused is a bad person who is therefore more likely to have committed the offences; 2) the jury may tend to punish the accused for his prior misconduct through a guilty verdict; and 3) the jury may have their attention deflected from the main purposes of the trial through litigation of the facts of the prior misconduct.
 In Pollock, Rosenberg J.A. explained that this risk of prejudice leads to the need for trial judges to consider the probative value of such evidence, the purposes for which it is sought, and the requirement that there be some evidentiary foundation to justify the need for the evidence sought, at para. 106:
Accordingly, since evidence of propensity or bad character can carry a very grave risk of prejudice to the fair trial of the accused against whom the evidence is led, it is incumbent on the trial judge to examine closely the probative value of the evidence and the purposes for which the evidence is tendered. In my view, in a joint trial, counsel’s mere assertion that the evidence is necessary for the accused to make full answer and defence is not sufficient given the grave potential for prejudice to the fair trial of a co-accused. There must be some evidentiary foundation to support this assertion. That foundation may come during the Crown’s case through evidence of Crown witnesses in chief or through cross-examination. In some cases, the evidentiary foundation may not be laid until the defence case. If so, the prejudicial character evidence would only be admissible, if at all, at that time. The need for this evidentiary foundation is not simply to avoid irrelevant evidence entering the record. An evidentiary foundation is essential to ensure fair management of the trial. The need for the highly prejudicial evidence can be properly assessed only when the accused demonstrates through evidence the contours of the defence. Until then, the trial judge is left to speculate on the importance and necessity of this evidence. [Emphasis added.] In R. v. Sheriffe, 2015 ONCA 880, 333 C.C.C. (3d) 330, at paras. 65-66, leave to appeal refused,  S.C.C.A. No. 299, this court elaborated on the analysis to be undertaken by a trial judge, in light of Pollock, where one co-accused seeks to elicit evidence from another that could not have been elicited by the Crown:
The risk of prejudice to the accused against whom bad character evidence is adduced is not attenuated because the evidence is elicited by a co-accused rather than by the Crown: Pollock, at para. 105. The trial judge must therefore still examine closely the probative value of the proposed evidence and the purposes for which it is adduced. A sound evidentiary foundation is essential: Pollock, at para. 106; Earhart, at para. 75. Likewise, a careful balancing of the fair trial rights of the two (or more) accused: Suzack, at para. 111; Pollock, at paras. 106-107; Diu, at para. 137. To repeat, consistent with general principles applicable to the discretionary exclusion of defence evidence developed in R. v. Seaboyer, 1991 CanLII 76 (SCC),  2 S.C.R. 577, at paras. 41-43, the standard in conducting this careful balancing of fair trial rights requires that relevant defence evidence offered by an accused relating to the character of a co-accused will be admissible unless its probative value is substantially outweighed by its prejudicial effect.
 The key issues in deciding whether the trial judge committed any errors on the Pollock application, therefore, are how the trial judge assessed the evidentiary foundation for the proposed cross-examination, the probative value and prejudicial effect of the cross-examination evidence sought by counsel for Mr. Bigby, and in light of this assessment, how he balanced the fair trial rights of Mr. Bigby and the appellant.