Every court agrees that litigants asserting their attorney-client privilege or work product protection must prove those protections' applicability. But as in so many other areas, courts recognize differences in determining who must carry the burden of proving waiver. All or nearly all courts require litigants asserting the attorney-client privilege to prove that they have not waived that fragile protection.

In Pipeline Productions, Inc. v. Madison Companies, LLC, the court held that once a litigant claiming work product protection establishes the protection's applicability, "the burden shifts to the party asserting waiver to establish that a waiver has occurred." Case No. 15-4890-KHV-ADM, 2019 U.S. Dist. LEXIS 142721, at *10 (D. Kan. Aug. 22, 2019). The court pointed to an earlier District of Kansas case holding that "in contrast to the attorney-client privilege, 'a party asserting work-product immunity is not required to prove non-waiver.'" Id. (citation omitted).

Although lawyers and even courts frequently use the generic term "privilege" to mean both attorney-client privilege and work product protection, there are many significant (and sometimes even case-dispositive) differences between those two protections.