Successfully admitting expert testimony can be a game-changer in litigation, but it requires careful attention to legal standards and preparation. As a forensic accounting expert with experience in intellectual property infringement and other damages claims and rebuttal, I’ve seen how crucial these steps can be to ensuring the admissibility of expert opinions. Below are seven tips to strengthen your case—and legal grounds on which opposing counsel could move to disallow expert testimony if these tips are overlooked.
1. Understand the Admissibility Standards (Daubert & Frye)
Legal Risk: If the methodology used by your expert doesn’t meet the required standard, the court may deem the testimony inadmissible. For example, see Waymo v Uber et al.
Under the Federal Rules of Evidence, particularly Rule 702 (expert witness testimony) federal courts and many states have adopted the so-called "Daubert Standard." Under Daubert, an opposing party can argue that the methods used are not scientifically valid, are not based on sufficient data, or have not been subject to peer review. This standard tends to be strict in ensuring that the expert's methodology is sound and applicable. Please click here to learn more about the Daubert Standard.
Some states, including California (at least historically), instead follow the so-called "Frye Standard," a test which requires that the expert’s testimony be based on scientific methods that are “generally accepted” in the relevant field. Frye is seen as a more lenient standard than Daubert in some respects. Please click here to learn more about the Frye Standard.
2. Choose the Right Expert
Legal Risk: If your expert’s qualifications are insufficient, opposing counsel could challenge them under Federal Rule of Evidence 702 or an equivalent local statute. They may argue that the expert lacks the necessary education, experience, or training in the relevant field, thereby disqualifying their testimony. This point merits its own blog post, perhaps.
3. Establish Relevance Early-On
Legal Risk: Testimony must assist the trier of fact in understanding or determining a fact at issue. Under Federal Rule of Evidence 702(a), opposing counsel may argue that the expert’s testimony is irrelevant if it does not directly relate to the issues of the case or if it fails to address a matter outside the common understanding of a layperson. Ensure that the expert is clear on the scope of their deliverable, especially with respect to supplementary or rebuttal reports.
4. Thoroughly Vet Your Expert’s Methods
Legal Risk: As mentioned above, if the methodology your expert relies on is questionable, Daubert or other motions can be used to exclude testimony on the grounds that it lacks reliability or scientific validity. Opposing counsel may argue that the expert’s techniques are speculative or insufficiently tested, or that they fail to meet professional standards. Therefore, take measures to ensure your experts are complying with the standards you designate. I recommend you research recent and historic case law because outdated or discredited methodologies can lead to the exclusion of expert testimony under Daubert. Opposing counsel may argue that the expert relied on outdated science, recent case law rejecting the methodology, or new standards that call into question the validity of the expert’s approach.
5. Require a Detailed Expert Report (or Declaration)
Legal Risk: A weak or vague expert report is vulnerable to attack under Federal Rule of Civil Procedure 26(a)(2)(B), which requires a complete statement of all opinions and the basis for those opinions. Opposing counsel may file a motion to exclude testimony on the basis that the expert report is incomplete, unsupported by sufficient facts, or based on inadmissible information.
However, state laws differ. In California, experts are not required to prepare written reports as part of the discovery process in state court. This is in contrast to federal court, where Rule 26 of the Federal Rules of Civil Procedure mandates expert reports.
The relevant statute in California is California Code of Civil Procedure (CCP) § 2034.210-2034.310. Under this statute, parties are required to disclose the identity of expert witnesses they intend to call at trial, along with a declaration summarizing the expert’s qualifications, a general substance of their testimony, and the expert’s hourly and daily fees for services; there is no statutory requirement for a detailed written report like there is under federal law.
Instead, in California state court, the discovery process involving experts focuses on depositions. During expert depositions, attorneys can probe the substance of the expert's anticipated testimony and the basis for their opinions. This approach allows for expert discovery without a formal report requirement.
Thus, in California, if an attorney requests expert opinions or methodologies, many an expert may disclose them through declarations or testimony, rather than a written report. That said, for a damages expert like myself who prepares complex calculations, I find I need to prepare, at minimum, report schedules/exhibits that set forth my calculations in order to testify about specific amounts and remind myself of the details.
6. Anticipate Challenges to Credibility & Prepare for Deposition and Trial Testimony
Legal Risk: Legal Risk: Inconsistent or poor testimony under cross-examination can damage an expert’s credibility, leading to a motion to strike the testimony as unreliable. Opposing counsel could file a motion under Federal Rule of Evidence 702(d), claiming that the expert has not reliably applied their methods to the facts of the case or challenging an expert’s credibility by pointing to prior inconsistent statements, or limited experience in the field. I suggest role playing with your expert to ensure they know how to respond to credibility attacks and your direct examination at minimum.
7. Emphasize Objectivity
Legal Risk: If your expert appears too aligned with your client’s case, they could be disqualified for appearing as an advocate rather than an independent professional. Opposing counsel may argue under Daubert or Federal Rule of Evidence 403 (which balances probative value against prejudice) that the expert’s bias renders their testimony unfairly prejudicial or untrustworthy. As part of this, do not engage the expert on a contingent basis - if they have a financial stake in the outcome of the case, their testimony can be excluded. This is one reason why my firm bills hourly.
Conclusion
Hopefully some of these tips will help you overcome challenges to your expert. For information about Boschan Corp.'s expert services, please click here or call us at 424-248-8866.
