R. v. Toth, 2024 BCCA 139, April 15, 2024, at paragraphs 27 to 29:

The first element of self defence under s. 34(1)(a) asks whether Mr. Toth believed, on reasonable grounds, that force was being used or threatened against him or his daughter. A modified objective test, where the accused’s beliefs are assessed from the perspective of an ordinary person who shares relevant attributes, experiences and circumstances of the accused, is to be applied to this inquiry…

Not all personal characteristics or experiences are relevant to the modified objective inquiry, as the objective standard is informed by contemporary norms of behaviour, not things such as personal prejudices or irrational fears. In general, an accused’s mental disabilities may be considered in the reasonableness assessment, as demonstrated in Nelson and Kagan: Khill at paras. 55–56. More recently, in R. v. Lawlor, 2023 SCC 34, the Court (both the majority and minority) emphasized that judges must be mindful of evidence as to mental health that is relevant to issues of criminal responsibility, especially when instructing a jury. This is so whether or not expert evidence is necessary to explain the relevance of a mental disability or condition to the issues at trial: see R. v. Lawlor, 2022 ONCA 645 at para. 134 per Justice Nordheimer dissenting, rev’d 2023 SCC 34 (substantially aff’g dissent of Nordheimer J.A. on this ground); see also R. v. Reeves, 2017 BCCA 97 at paras. 17–20.

In the context of a claim of self defence, evidence that a mental disability or condition could have affected an accused’s perception about force being used or threatened against them or another person will be relevant to the inquiry. The question here is not what Mr. Toth thought was reasonable based on his characteristics and experiences, but rather what a reasonable person with those relevant characteristics and experiences would perceive: Khill at para. 57.