Complex environmental litigation routinely requires attorneys to turn to experts for insight into scientific matters beyond the average lawyer’s competency. Indeed, it would be difficult for most lawyers to litigate CERCLA matters, for example, without assistance from both consulting and testifying experts. While the 2010 amendments to Federal Rule of Civil Procedure 26 provide more protection for attorneys’ communications with consulting experts than testifying experts, when a single expert serves in both roles, even informally, the risk that communications and materials may be subject to discovery grows. This article examines those amendments in the context of so-called “dual-hat” experts.
In 2010, the Federal Rules of Civil Procedure were amended to enhance protections on attorneys’ mental impressions in attorney-expert communications, particularly given searching discovery requests that hampered lawyers’ free consultation with their experts without fear of those communications being subject to discovery. While discovery pertaining to consulting experts is more circumscribed than for testifying experts, Employees Committed for J. v. Eastman Kodak Co., 251 F.R.D. 101, 104 (W.D.N.Y. 2008) (noting that materials reviewed or generated by a consulting expert “are generally privileged and immune from disclosure”), when a single expert serves in both a consulting and testifying capacity, the lines blur between what is protected and discoverable.
For testifying experts, Rule 26(a)(2)(B)(ii) requires disclosure of all “facts or data considered by the witness in forming” their opinions. Prior to 2010,[1] most courts interpreted Rule 26(a)(2) as requiring disclosure of all attorney-expert communications, including “otherwise protected work product and attorney-client communications” that the expert “read or reviewed before or in connection with formulating his or her opinion.” In re Commercial Money Ctr., Inc., Equip. Leasing Litig., 248 F.R.D. 532, 537 (N.D. Ohio 2008). That approach led to runaway discovery and impeded attorneys’ free communication with expert witnesses out of fear that those communications would wind up in their adversaries’ hands. See Fed. R. Civ. P. 26, Adv. Comm. Notes to 2010 Amendments. As a result, attorneys began to employ “two sets of experts—one for purposes of consultation and another to testify at trial,” especially in high value cases. Id. This approach—purely designed to sidestep Rule 26—proved costly and needlessly complex.
The 2010 amendments to Rule 26 were intended to rectify some of these issues by “excluding theories or mental impressions of counsel”— although not those of their testifying experts—from discovery. See Fed. R. Civ. P. 26(b)(4)(C), Advisory Comm. note to 2010 amendments; see also Republic of Ecuador v. Mackay, 742 F.3d 860, 870 (9th Cir. 2014) (“[T]he driving purpose of the 2010 amendments was to protect opinion work product—i.e., attorney mental impressions, conclusions, opinions, or legal theories—from discovery.”). Rule 26(b)(4) protects attorney communications with testifying experts from disclosure, except for communications that (1) relate to the expert’s compensation; (2) identify “facts or data provided by the party’s attorney that the expert considered in forming expressed opinions”; or (3) “identify assumptions provided to the expert by the party’s attorney and that the expert relied on . . . .” Fed. R. Civ. P. 26(b)(4)(C)(i)-(iii) (emphasis added). Only communications “identify[ing]” facts or data provided to a testifying expert are discoverable, Fed. R. Civ. P. 26(b)(4)(C)(ii), whereas communications regarding the “potential relevance of the facts or data are protected[,]” Fed. R. Civ. P. 26(b)(4) Advisory Committee Note to 2010 Amendments. This distinction protects attorneys’ mental impressions, requiring disclosure of instructions provided to testifying experts while shielding deliberative communications likely to reflect attorneys’ strategic thinking. In contrast, communications regarding assumptions an expert should rely on are discoverable to the extent that the expert “actually did rely” upon those assumptions in forming his or her opinions. Id.; see also Hood v. City of Chicago, 2021 U.S. Dist. LEXIS 263257, at *16-18 (N.D. Ill. Mar. 30, 2021) (permitting inquiry into materials counsel provided to expert and communications “surrounding the conveyance” of materials that the testifying expert considered, but allowing inquiry as to assumptions only to the extent counsel “convey[ed] that the expert should assume the truth of certain evidence”).
With respect to consulting experts, Rule 26 prohibits discovery of “facts known or opinions held by an expert . . . who is not expected to be called as a witness at trial.” Fed. R. Civ. P. 26(b)(4)(D). That rule provides a “safe harbor” shielding materials considered by non-testifying experts from discovery absent exceptional circumstances. Will Uptown, LLC v. B&P Restaurant Group, LLC, No. 15-51, 2016 WL 4620200, at *5 (M.D. La. Sept. 6, 2016).
In dual-hat expert cases, however, “the term ‘considered’ in Rules 26(a)(2)(B) [and (b)(4)(C)(ii)] should be construed expansively in favor of the party seeking discovery . . . .” Yeda Research & Dev. Co. v. Abbott GMBH & Co. KG, 292 F.R.D. 97, 108 (D.D.C. 2013). Only materials “generated or considered uniquely in the expert’s role as a consultant” are protected from disclosure. Sara Lee Corp. v. Kraft Foods, Inc., 273 F.R.D. 416, 419-20 (N.D. Ill. 2011) (emphasis added). That an expert is designated both to consult and testify “does not act to shield otherwise discoverable material . . . .” Williams v. First Student, Inc., 2023 U.S. Dist. LEXIS 27294, at *9 (D.N.J. Feb. 17, 2023) (internal quotation omitted).
The party resisting disclosure of a dual-hat expert’s materials must show that the sought-after information was not also considered “pursuant to the expert’s testifying function.” Bro-Tech, 2008 U.S. Dist. LEXIS 21233, at 11. To carry that potentially heavy burden, the resisting party must demonstrate that the expert could not have considered the materials in question or provide affidavits and/or deposition testimony showing that the expert did not “read, review[], or consider[] the subject documents in forming his opinions” to be presented at trial. Jacobson Warehouse Co. v. Prestige Brands, Inc., 2022 WL 1617711, at *3 (S.D.N.Y. May 23, 2022) (quotation omitted)). Representations from counsel or the expert alone are insufficient to preclude disclosure. Id.
The lodestar of courts’ analysis is the subject matter of materials an expert has considered, focusing on the substantive relationship between the expert’s duties as a consulting and testifying expert. Yeda, 292 F.R.D. at 113; see also Ictech-Bendeck v. Waste Connections Bayou, Inc., 2024 U.S. Dist. LEXIS 196001, at *50 (E.D. La. Jan 30, 2024) (noting a “presumption in favor of the party seeking discovery” when withheld documents “concern subject matter directly related to the opinion in the expert report”). If materials are relevant to the expert’s opinions, courts require disclosure when there is any ambiguity regarding whether the materials informed the expert’s opinions. See, e.g., Yeda, 292 F.R.D. at 108; B.C.F. Oil Refining, Inc. v. Consolidated Edison Co. of N.Y. Inc., 171 F.R.D. 57, 62 (S.D.N.Y. 1997). This ambiguity-based approach skews the analysis in favor of the requesting party, subjecting consultation-related communications and materials to discovery that would be protected if the expert were exclusively used as a consultant.
Some courts have concluded that any overlap in subject matter between an expert’s consulting and testifying roles warrants disclosure. See Clark v. Quiros, 2022 U.S. Dist. LEXIS 154800, at *25 (D. Conn. Aug. 29, 2022) (work product protection applies only “when there is no overlap between the expert’s consulting and testifying roles” (emphasis in original)). Others have taken a somewhat more lenient approach. See, e.g., Sara Lee, 273 F.R.D. at 420 (expert designated to testify on only one of two allegedly deceptive ads at issue in the case; communications related to the other ad were not subject to disclosure).
Even after the 2010 Amendments, courts have repeatedly compelled disclosure of materials where there is any overlap between subject matter in consultation and testimonial materials. This formalism is often at odds with the practical realities of complex litigation, in which practitioners seek informal, as-needed advice from their testifying experts rather than having a separate consulting expert on call to assess every scientific triviality that might arise.
So what should practitioners do to protect against disclosure of their dual-hat experts’ consultative assessments? Courts’ square focus on the subject matter of a consulting expert’s work compared to their testimony means that merely keeping separate files for each role is insufficient to protect relevant consulting materials against disclosure. Unfortunately, the safest course remains to retain a separate consulting expert for assistance, which is often impractical and cost prohibitive. Avoiding putting consultative communications in writing is helpful at reducing paper discovery, but testifying experts may still be deposed regarding those communications if the subject matter overlaps with their testimony.
Courts’ broad interpretation of what materials a testifying expert “considers” in forming his or her opinions has led us back to where we started. If the Federal Rules are ever to reduce the procedural hoops attorneys must navigate to safeguard factual materials provided to dual-hat experts for consulting purposes, further amendments to Rule 26 will be required.
[1] The 2010 Amendments substituted “facts or data” for “data or other information” in order to “alter the outcome in cases . . . requiring disclosure of all attorney-expert communications and draft reports.” Fed. R. Civ. P. 26(a)(2)(B)(ii), Advisory Committee Note to 2010 Amendments.
For questions, please contact author Louis Dodge at dodge@lssh-law.com.