In The Republic of Ecuador v. Mackay, the Ninth Circuit limited the protection afforded to testifying experts’ materials under Federal Rule of Civil Procedure 26(b)(3). The case involved claims brought by a group of Ecuadorians for alleged damages caused by drilling-related pollution and contamination. The materials consisted of work from defendant Chevron’s experts on the topics of soil and groundwater conditions and epidemiology. Chevron argued that Rule 26(b)(3) “always provides presumptive protection for all testifying expert materials because they are necessarily prepared ‘by or for’ a party or its representative.” The Ninth Circuit’s three-judge panel disagreed, however, affirming the district court’s opinion and describing Chevron’s arguments as “redundant” and “implausible.” The court found that the evolution of Rule 26(b)(3) and the related Advisory Committee notes are intended to protect work-product, including draft reports and attorney-expert communications. However, the court concluded that opposing parties have a right to “understand and respond to a testifying expert’s analysis” and that the failure to provide trial preparation materials that contain that information “would hamper an adverse party’s ability to prepare for cross-examination and rebuttal.”