R. v. Osman, 2022 ABCA 77, March 2, 2022, at paragraphs 95 and 96:

Among other things, Ms Pascal testified that she heard yelling and a voice saying “no” coming from the laundry room at the Wheyee residence on the night in question. At the time, Ms Pascal was in T Wheyee’s bedroom and could not see into the laundry room. Crown counsel asked her what she thought was going on and two of the defence counsel objected because the answer would be inadmissible, either because it was irrelevant or required speculation (since she was not in the laundry room). After hearing argument, the trial judge allowed the question and Ms Pascal testified that she thought “they were confronting someone in the house”.

On appeal, T Wheyee argues that Ms Pascal’s answer was inadmissible for a slightly different reason – it was opinion evidence and Ms Pascal was not an expert. This argument assumes that a lay witness can never give evidence interpreting her own observations or auditory experiences. In fact, the law is more nuanced than that. Following R v Graat, 1982 CanLII 33 (SCC), [1982] 2 SCR 819, 2 CCC (3d) 365, a lay witness may give an opinion interpreting her observations or experiences if the opinion is merely a “compendious way” of describing the facts perceived and, without giving the opinion, the witness could not as accurately or adequately describe the events perceived. Such evidence may also be admissible as within the observational capacity of an ordinary person: R v Awer, 2016 ABCA 128 at para 35, reversed on other grounds but (arguably) not on this point 2017 SCC 2 at para 2.