- the communications must originate in a confidence that they will not be disclosed.
- this element of confidentiality must be essential to the full and satisfactory maintenance of the relation between the parties.
- the relation must be one which in the opinion of the community ought to be sedulously fostered.
- the injury that would inure to the relation by the disclosure of the communications must be greater than the benefit thereby gained for the correct disposal of litigation.
(Wigmore, 1905; italics in original)
See Palys & Lowman (2000) for consideration of how the Wigmore criteria apply to the researcher-participant relationship.