What is the test for drawing an adverse inference when a party fails to call a witness?

The basic legal principles that apply when the court is asked to draw an adverse inference are discussed in Singh v. Reddy, 2019 BCCA 79, at paras. 8 and following, and also Wu v. Gu, at paras. 107 and following. The court is not required as a matter of law to draw an adverse inference where a party fails to call a witness. The approach to drawing an adverse inference engages the court’s discretion and requires the trier of fact to consider: (a) whether there is a legitimate explanation for failing to call the witness; (b) whether the witness is within the exclusive control of the party or is equally available to both parties; and (c) whether the witness has key evidence to provide or is the best person to provide the evidence in question.