What is the threshold test for cross-examining in a sexual assault case?

He then went on to establish the operative threshold test: "In my opinion, the preconditions in Franks v. Delaware supra, are too restrictive. I believe that they are inconsistent with the approach which we have taken in Canada with respect to the right to cross-examine. Moreover, subject to the protection of the identity of informants and the concern with respect to the prolongation of proceedings, I see no reason for such a drastic curtailment of the right. I believe these concerns can be accommodated without imposing restrictions as inhibitive as those in Franks v. Delaware. With respect to informants, there is no right to cross-examine them. The informant is not a witness and cannot be identified unless the accused brings himself within the "innocence of stake" exception. "With respect to prolixity, I am in favour of placing reasonable limitations on the cross-examination. Leave must be obtained to cross-examine. The granting of leave must be left to the exercise of the discretion of the trial judge. Leave should be granted when the trial judge is satisfied that cross-examination is necessary to enable the accused to make full answer and defence, A basis must be shown by the accused for the view that the cross-examination will elicit testimony tending to discredit the existence of one of the preconditions to the authorization, as, for example, the existence of reasonable and probable grounds. "When permitted, the cross-examination should be limited by the trial judge to questions that are directed to establishing that there was no basis upon which the authorization could have been granted. The discretion of the trial judge should not be interfered with on appeal except in cases in which it has not been judicially exercised. While leave to cross-examine is not a general rule, it is justified in these circumstances in order to prevent an abuse of what is essentially a ruling on the admissibility of evidence." (my emphasis)