What is the test for disclosing privileged information?

While the judge is determining whether the privilege applies, all caution must be taken on the assumption that it does apply. This means that under no circumstances should any third party be admitted to the proceedings, and even the claim of informer privilege must not be disclosed. The only parties admitted in this part of the proceeding are the person who seeks the protection of the privilege and the Attorney General. It is the responsibility of the judge at this stage to demand from the parties some evidence which satisfies the judge, on balance, that the person is a confidential informer. Once it has been established on the evidence that the person is a confidential informer, the privilege applies. I cannot overemphasize the importance of this last point. The judge has no discretion not to apply the privilege: Bisaillon v. Keable [1983 CanLII 26 (SCC), [1983] 2 S.C.R. 60], at p. 93. If the person is an informer, the privilege applies fully. …