The ancient attorney-client privilege protection provides absolute but fragile immunity from discovery. The relatively new litigation-related work product doctrine provides limited but robust immunity from discovery. Lawyers should always be on the lookout for both types of protection.

Another more subtle distinction plays a role in litigation over these protections. In Luckenbach Texas, Inc. v. Skloss, No. 1:21-CV-00871-RP, 2023 U.S. Dist. LEXIS 36506, at *6-7 (W.D. Tex. Mar. 6, 2023), the court recognized that "[t]he burden of proving waiver of the work product privilege falls on the party asserting waiver" (quoting an earlier case). Four days later, the court in Boines v. JARS Cannabis, LLC, articulated the universal rule that "[t]he burden of establishing the attorney-client privilege rests with the party asserting it" — "unless the protection is waived." Case No. 2:21-cv-13010, 2023 U.S. Dist. LEXIS 41070, at *5 (E.D. Mich. Mar. 10, 2023) (citations omitted).

Most courts similarly: (1) require a litigant challenging an adversary's work product claim to prove waiver while (2) requiring a litigant asserting attorney-client privilege protection to prove lack of waiver. This conceptual distinction could have practical consequences in discovery disputes.