Though both the Daubert and Frye standards leave room for differing methodologies from different fields, neither standard adopts an “anything goes” approach. Rather, both delineate criteria for evaluating a particular expert witness’s methodology in court. Expert witnesses who understand how these standards function to analyze admissible methodology will be well prepared for a smooth expert qualification process.
Recognizing Reliable Expert Methodology Under Daubert
In Daubert v. Merrell Dow Pharmaceuticals, the U.S. Supreme Court set out several criteria for determining whether an expert witness’s methodology is based on sufficiently valid scientific or technical reasoning and may be properly applied to the case at hand. These criteria were later incorporated into Federal Rule of Evidence 702.
The Daubert factors include:
- Whether the theory or technique in question can be and has been tested
- Whether the theory or technique has been subjected to peer review and publication,
- Its known or potential error rate
- Whether there exist standards to control its operation, and if so, how these standards are maintained
- Whether the theory or technique has received broad acceptance within the relevant scientific, technical, or professional community.
Six years later the Daubert decision, in Kumho Tire, Inc. v. Carmichael, the Supreme Court clarified that the Daubert standard may also be applied to non-scientific expert testimony, such as testimony on technical points given by an engineer.
Under the Daubert standard, courts must determine the validity of an expert witness’s methodology. To assist a court in making this determination, an attorney who submits an expert witness must be prepared to show that the expert’s methodology is valid both as it is applied to the facts of the case at hand and in the broader context of the expert’s professional community.
Recognizing Reliable Expert Methodology Under Frye
For decades prior to the U.S. Supreme Court’s decision in Daubert, expert witness methodology had to survive the standard set forth in Frye v. United States—a standard still relied upon in some US state courts today.
In Frye, the court stated that an expert witness’s methodology, or “the thing from which the deduction is made,” must be “sufficiently established to have gained general acceptance in the particular field in which it belongs.” Under Frye, the court’s focus is on the expert’s methodology within the context of the expert’s own field, rather than in the context of the facts at issue. A Frye hearing typically focuses on novel scientific evidence. The analysis in a Frye hearing is thus more limited than that of a Daubert hearing.
Tips at Trial: Staying on Track for Qualification
Whether Daubert or Frye provides the standard, it is important for expert witnesses to prepare for questions regarding their methodology. Lay a foundation with research performed well in advance of any anticipated hearing date. Examples of peer-reviewed literature from an expert’s field that support the methodology used can help contextualize that methodology under either expert witness standard. By pointing to other work done in the field on the same topic, an expert witness can put their own work in context for attorneys and judges.
On top of having research credentials handy, don’t shy away from mentioning your own publications, if they are relevant. Scientific publications typically face rigorous peer review and adherence to “generally accepted” methodologies increases the chances of a paper’s publication. As such, peer-reviewed publication increases the chances of an expert’s methodologies being accepted under either Daubert or Frye. The act of publication itself can also serve as evidence that an expert’s methodology has been tested, as well as peer-reviewed. Some publications even discuss matters like error rates and standards of measurement.
Similarly, be willing to refer to your own CV when needed, particularly your memberships in professional organizations. Be prepared to discuss those organizations’ methodological standards, if any, and how you have adhered to them in your work on the case. If you deviated from those standards, be prepared to explain why.
As an expert, it’s also important to embrace the nuances of scientific and technical language regarding certainty. The Daubert factors account for the fact that no scientific fact can be known with absolute certainty; Frye only asks that an expert’s methods be “generally” accepted. An expert witness who can candidly discuss error rates, margins of error, and competing hypotheses or explanations will often increase rather than decrease their own credibility.
Finally, be sure you gather all the relevant records and information from the attorney before you begin your expert analysis. Having all the information helps experts avoid missing information that might be critical to their choice of methods or analysis. While writing an expert witness report, avoid drawing legal conclusions. Instead, stick to the facts while conducting a thorough analysis and whenever possible, base qualitative discussions on quantitative data. With a basic understanding of the applicable standards, expert witnesses are well-positioned for making informed choices regarding methodology and ensuring their qualification.