How have courts treated the issue of interviewing witnesses in civil cases?

The issue of interviewing witnesses was addressed in Tessier v. Nova Scotia (Human Rights Commission), 2014 NSSC 65, [2014] N.S.J. No. 76, where certain witnesses referred to by the complainant had not been interviewed. In Egan v. Canada (Attorney General), 2008 FC 649, [2008] F.C.J. No. 816, Hughes J. said, “where a reasonable person would expect that useful evidence could possibly be gained by an interview there is some obligation to conduct the interview or say why not” (para. 24). By contrast, Nadon J. adopted a higher standard in Slattery, holding that no breach of procedural fairness will be found unless the witness could have provided “obviously crucial evidence” (para. 56).