An adverse inference in the context of a failure to call a witness

R. v. Rudge, 2011 ONCA 791 has a useful discussion of when an adverse inference may be drawn by a failure to call a witness:

[78]         The Supreme Court of Canada addressed the issue of an adverse inference in the context of the Crown's failure to call a witness in R. v. Jolivet, [2000] 1 S.C.R. 751.  The general rule, applicable in both civil and criminal cases, is that all evidence is to be weighed according to the proof that one side is capable of producing and the other side is capable of contradicting. In the criminal context, the general rule is subject to many conditions to account for the peculiar division of responsibilities between the Crown and the defence. First, the party against whom an adverse inference is sought may provide a satisfactory account for its failure to produce a witness (para. 26).  Second, there is a stronger basis for the drawing of an adverse interest where one party has special access to the potential witness (para. 27). Additionally, attention must be paid to the exact nature of the adverse inference sought to be drawn.  Binnie J. stated the following, at para. 28:

In J. Sopinka, S. N. Lederman and A. W. Bryant, The Law of Evidence in Canada (2nd ed. 1999), at p. 297, para. 6.321, it is pointed out that the failure to call evidence may, depending on the circumstances, amount "to an implied admission that the evidence of the absent witness would be contrary to the party's case, or at least would not support it", as stated in the civil case of Murray v. Saskatoon, [1952] 2 D.L.R. 499 (Sask. C.A.), at p. 506. The circumstances in which trial counsel decide not to call a particular witness may restrict the nature of the appropriate "adverse inference". Experienced trial lawyers will often decide against calling an available witness because the point has been adequately covered by another witness, or an honest witness has a poor demeanour, or other factors unrelated to the truth of the testimony. Other jurisdictions also recognize that in many cases the most that can be inferred is that the testimony would not have been helpful to a party, not necessarily that it would have been adverse". [Emphasis added by Binnie J. Citations omitted].