The Wigmore Criteria

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.

For the most part, this criterion would be met via expert testimony. Many possible communities to consider, including:

4. 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.