Unlike the very fragile attorney-client privilege (which can be waived even by disclosure to family members), the more robust work product doctrine protection survives disclosure to friendly third parties.

Most courts understand this. In Pfizer Inc. v. Regor Therapeutics Inc., the court correctly understood that "[t]he work product doctrine has a different rationale [from the privilege], and therefore presents different waiver considerations.... A party therefore waives work product protection when it discloses those thought processes to its adversary, and when it discloses them to a non-adversary in a way 'that substantially or materially increases the likelihood that adversary will obtain the information.'" Civ. No. 3:22-cv-00190 (JAM), 2023 U.S. Dist. LEXIS 18898, at *14 (D. Conn. Feb. 3, 2023) (citation omitted). But some courts don't get it — demanding that those sharing work product satisfy the rigorous common interest doctrine prerequisites. For instance, in Cotter v. Eighth Judicial District Court, the Nevada Supreme Court insisted that "[f]or the common interest rule to apply, the 'transferor and transferee [of work product] [must] anticipate litigation against a common adversary on the same issue or issues' and 'have strong common interest in sharing the fruit of the trial preparation efforts.'" 416 P.3d 228, 232 (Nev. 2018) (en banc) (second alteration in original) (citation omitted).

The very demanding common interest doctrine prerequisites to avoid waiver apply only to the fragile privilege protection — not to the work product doctrine protection. Lawyers must be prepared to explain this key distinction to courts that improperly equate the two evidentiary protections.