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Daubert-Proofing Your Expert

Ebony S Morris


  • Expert testimony in mass tort litigation must meet the standards set by Daubert, which require scientific knowledge and evidentiary reliability.
  • Courts consider four factors when determining the admissibility of expert testimony: testability, peer review, error rate, and acceptance in the relevant scientific community.
  • Practitioners should highlight the qualifications of their expert, demonstrate the reliability of their expert's opinion through data and methodologies, and be familiar with the literature relied upon by their expert.
  • Retaining qualified experts who conduct thorough and objective research is crucial to successfully navigating Daubert challenges.
Daubert-Proofing Your Expert
Courtney Hale via Getty Images

Mass tort litigation often involves a battle of expert witnesses. When the crux of your case depends on expert testimony, it is crucial to be able to survive Daubert challenges. In Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 590 (1993), the U.S. Supreme Court held that the subject of an expert’s testimony must be founded upon “scientific knowledge” and that this requirement established a “standard of evidentiary reliability.” The Court further explained that the “scientific knowledge” requirement means that the expert’s opinion must be more than subjective belief or mere speculation. Daubert allows a court to act as a “gatekeeper” of expert testimony and play a more active role in shaping the admissibility of trial testimony. The gatekeeping function is intended to ensure that any and all scientific testimony or evidence admitted is relevant and reliable.

Under Daubert, the Court considers four factors to when determining the admissibility of expert testimony:

  1. whether the theory can and has been tested;
  2. whether it has been subject to peer review;
  3. the known or expected rate of error; and
  4. whether the theory or methodology employed is generally accepted in the relevant scientific community.

Under Daubert’s progeny, scientific expert testimony is admissible when the testimony meets the following three-part test:

  1. the proffered witness must be an expert. i.e., the witness must be qualified;
  2. the expert must testify about matters requiring scientific, technical, or specialized knowledge; and
  3. the expert’s testimony must assist the trier of fact. See Kannankeril v. Terminix Int’l Inc., 128 F.3d 802, 806 (3d Cir. 1997).

To survive a Daubert challenge, practitioners should consider the following practices.

Highlight Your Expert’s Qualifications

It is a given that the expert must be qualified to serve as an expert witness to render an opinion in your case. Attaching a detailed curriculum vitae in response to a Daubert challenge is absolutely necessary. All published and peer-reviewed literature should be noted in the response. The expert’s ability to proffer peer-reviewed articles as authority to support his/her opinions weighs heavily on a judge’s determination to grant or deny a Daubert motion. In Daubert, the Court stated that “peer review[ed]” is significant because “scrutiny of the scientific community is a component of ‘good science’ in part because it increases the likelihood that substantive flaws in methodology will be detected.” Daubert, 509 U.S. at 593. Weighing the credibility of the expert falls within the province of the jury as the fact finder. Be prepared to argue that if your expert meets the liberal minimum qualification requirement, then “the level of the expert’s expertise goes to credibility and weight, not admissibility.” Kannankeril, 128 F.3d 802 at 809.

Illustrate the Reliability of Your Expert’s Opinion

The foundation of Daubert is being able to demonstrate that the expert’s opinion by using sufficient data that utilizes reliable principles and methodologies that can be reproduced by independent testing. If another expert cannot replicate your expert’s analysis, you will not survive a Daubert challenge. The importance of this cannot be overstated. For example, in Lock Realty Corp v. U.S. Health, U.S. District Court, N.D. Indiana, South Bend Division, 2009 WL 2970330, the court excluded the plaintiff’s expert from testifying in a breach of contract claim. The expert’s opinion was based on two emails between the parties and a Medicaid valuation of fair market value. The court took issue with the reliability of the expert’s methodology and excluded portions of the expert’s report. Id. at *12.

Know the Literature

Take the time to learn the literature relied upon by your expert witness. Carefully reviewing all of the articles your expert has published will not only in make you able to articulate the reliability of your expert’s testimony, but will allow you the opportunity to spot any inconsistencies in your expert’s opinion in your case and what your expert may have opined in the past. Your expert’s peer-reviewed literature should also provide you with ample material to cross-examine your opponent’s expert witness.

Retaining expert witnesses is a costly part of litigation; however, expert witnesses play an important role in molding a case’s theory. To survive Daubert, we must retain qualified experts whose theories can be tested, and experts who are willing to invest time and effort in conducting thorough and objective research prior to issuing a written expert report.