The theory of this test is that the courts may balance the public interest in maintaining the privilege against the interest the court may have in pursuing the truth. The Wigmore test for determining whether a communication is privileged was adopted in R. v. Fosty
(sub. nom. R. v. Gruenke ),  3 S.C.R. 263 at p. 284:
1) The communications must originate in a confidence that they will not be disclosed.
2) This element of confidentiality must be essential to the full and satisfactory maintenance of the relation between the parties.
3) The relation must be one which in the opinion of the community ought to be sedulously fostered.
4) The injury that would inure to the relation by the disclosure of the communication must be greater than the benefit thereby gained for the correct disposal of litigation ...
[Emphasis in Original]
Lamer C.J.C. states in [R. v. Fosty] that Wigmore's test may be used as a “general framework” to assess whether a communication should be privileged on a case by case basis.
The defendants must meet all four elements of the test to successfully assert the privilege.
Bank of British Columbia v. Canadian Broadcasting Corp. |
1993 CarswellBC 698 at para. 37 |
38 Maczko J.