The common interest doctrine creates an oftentimes frustrating exception to the general rule that disclosure of information to a party outside of the normal attorney-client relationship destroys privilege. Essentially, it extends the attorney-client privilege and the work product doctrine so that, in certain situations, privileged communications and documents may be shared with third parties without waiver when the parties share similar legal interests. It can be a powerful tool when used to block discovery of relevant and sometimes critical evidence. However, a determination of when the common interest doctrine can be invoked requires a highly fact-intensive analysis. To that end, a recent letter opinion by Judge Laurie Silverstein of the U.S. Bankruptcy Court for the District of Delaware provides a helpful review of the standard for the assertion of the common interest privilege in the context of a plan discovery fight. See. In re Imerys Talc America, 2021 Bankr. LEXIS 428 (Bankr. D. Del. Feb. 23, 2021).