What is the test for calling a substantive defence at trial?

In United States of America v. Mach, [2006] OJ No. 3204 at para. 19, Trafford J. reaffirmed that evidence that tends to exonerate the accused, or contradicts the requesting state’s case for the prosecution [such a as a substantive defence], but does not specifically undermine the reliability of that case cannot be weighed or considered by the extradition judge: The notion of manifest unreliability articulated by the court in United States of America v. Ferras …requires a body of evidence that directly undermines the reliability of the evidence in the record of case presented by the requesting state. The calling of the defence, as it would be at trial, is not what is contemplated under United States of America v. Ferras.