Federal Rule of Evidence 702 governs the admission of expert testimony. Rule 702 allows testimony to be admitted if the scientific, technical, or other specialized knowledge within that testimony will help the trier of fact make sense of the evidence or understand the facts. In its ruling for Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993),the Supreme Court established that judges are the "gatekeepers" against "junk science."
Federal Rule of Civil Procedure 26, which outlines the requirements and limitations of expert-witness disclosures, was substantially amended on December 1, 2010. Prior to 2010, Rule 26 was last amended in 1993. The Advisory Committee notes supplementing the 1993 amendment clarified that, from that point on, experts were required to disclose any and all data used in formulating their opinions. This was to include drafts and information that an expert might have rejected or not considered at all, thus preventing parties from claiming privilege over materials prepared by experts in the process of formulating their testimony. Since the 1993 amendment, most federal courts have borrowed the reasoning from the committee notes in ordering experts to disclose all draft reports and any communications that an expert has had with counsel.
These requirements led lawyers to adopt the practice of having little to no written correspondence with their experts to avoid creating discoverable information. This impractical custom came with drawbacks. On the one hand, lawyers could not freely communicate and exchange ideas with their experts, which, in turn, hindered the quality of an expert's analysis. Moreover, to ensure that they had the most sophisticated expert testimony, lawyers would frequently hire multiple experts—a testifying and a nontestifying expert. The nontestifying expert would act as the agent between the lawyer and the testifying expert by "guiding" the opinion of the testifying expert to comply with the lawyer's strategy. This process of purposefully exploiting the loophole created by the 1993 amendment translated into increased costs for clients.