What is the test for drawing adverse conclusions from failing to call a witness?

The Court in McIlvenna v. Viebig, 2012 BCSC 218, at paragraphs 71 to 74, also addressed the issue of adverse inferences arising from failure to call witnesses. It referred to some of the factors which are relevant to determining whether or not to draw adverse inferences. They include the following: 1. whether there is a legitimate explanation for failing to call the witness; 2. whether the witness is in exclusive control of one party or available to both; 3. whether the witness can provide key evidence or is the best person to provide it; 4. the nature of the evidence that could be provided; and, 5. the extent of disclosure made to the other party.