What is the legal test for privilege over privileged documents?

10. The question in each case is how large the “protected area” needs to be to facilitate the adversarial process. As many decisions from various levels of courts have pointed out, solicitor-client privilege protects a relationship and is therefore inviolable and unlimited. Litigation privilege protects a process. Like any form of privilege, it removes from view evidence that would otherwise be relevant and admissible, and hence limits the ability of the parties and the adjudicator to ascertain the truth of the facts of a case. Hence, the exclusionary rule should be no broader than is required to protect the process itself. As noted in Blank v. Canada, above, litigation privilege disappears when the litigation is complete.