R. v. Salman, 2023 ABCA 107, April 11. 2023, at paragraphs 8 to 11:
On appeal, the appellant submits that Chris would have been able to provide important evidence and that the Crown provided no explanation for the failure to call him. While he acknowledges that the trial judge was not required to draw an adverse inference, the appellant argues that the trial judge’s “refusal to turn his mind to the absence of important evidence” was an error that justifies this Court’s intervention. We disagree.
As was recognized in R v Jolivet, 2000 SCC 29 at para 14, “the Crown is under no obligation to call a witness it considers unnecessary to the prosecution’s case.” There may be cases where “[t]he failure of the Crown to call a witness may leave a gap in the Crown’s case which will leave the Crown’s burden of proof undischarged and entitle the accused to an acquittal”: R v Yebes, 1987 CanLII 17 (SCC),  2 SCR 168 at 190. This, however, is not such a case.
The appellant’s argument essentially comes down to a suggestion that the trial judge should have speculated about possible inconsistencies between the evidence Chris may have given and the evidence of the complainant. Even if one were to engage in this type of speculation, at best the areas where possible inconsistencies might arise relate only to matters collateral to the elements of the offence. The complainant admitted to some such inconsistencies in her evidence, and they were the focus of cross-examination. The trial judge considered those inconsistencies and did not find that they raised a reasonable doubt.
In our view, the trial judge’s refusal to engage in the type of speculation now suggested by the appellant does not disclose reviewable error.