Objections to Expert Testimony: What You Need to Know

Anjelica Cappellino, J.D.

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— Updated on August 10, 2021

Objections to Expert Testimony: What You Need to Know

Expert testimony is a major component of successful litigation. However, there are instances where the court may deem an expert’s testimony is inadmissible or may largely curtail its scope. In these cases, expert testimony may be rendered useless. For these reasons, it’s important to be mindful of the ways an expert’s testimony can be challenged. Whether you are seeking to admit your own expert or arguing against your adversary’s, these are the most salient factors to consider on the admissibility front.

Know the Governing Standard

Every jurisdiction has a different standard for expert admissibility. But generally speaking, most states either follow some variation of the Daubert or Frye tests. The Frye test is based on the D.C. Circuit case, Frye v. United States, 293 F. 1013 (D.C. Cir. 1923). Here, the court held that an expert opinion is admissible if the scientific technique utilized is “generally accepted” as reliable in the relevant scientific community. Commonly referred to as the “general acceptance” test, a number of states follow this standard, which focuses on the consensus of the expert’s own community.

Decades later, the United States Supreme Court set forth a competing standard in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). Here, the court listed several factors to consider when determining the admissibility of an expert. Like Frye, Daubert also includes general acceptance within the scientific community. In addition, the court also asks:

  1. Whether the expert’s technique or theory can undergo testing and assessment for reliability
  2. Whether the technique or theory has been subject to peer review and publication
  3. The known or potential rate of error of the technique or theory
  4. The existence and maintenance of standards and controls.

Approximately 27 states use some version of the Daubert test. The Daubert standard is also utilized in federal court, codified in Rule 702 of the Federal Rules of Evidence. There remains no evidence that one standard is stricter than the other. This is despite several studies conducted on the topic. It is nonetheless critical to know the standard within your practicing jurisdiction and tailor your arguments accordingly.

Motions In Limine

The battleground for expert admissibility typically begins well in advance of trial. Typically, parties are obligated to provide a disclosure notice if they intend to use an expert. In the federal context, this is governed by Rule 26 of the Federal Rules of Civil Procedure and Rule 16 of the Federal Rules of Criminal Procedure.

Therefore, if you intend to object to the entirety (or a portion) of your opposing party’s expert, it is helpful to make those arguments via a motion in limine. This is a pre-trial motion requesting the exclusion of certain testimony or evidence. Disclosure of the opposing expert’s entire testimony won’t occur at this stage. However, this notice requirement should provide sufficient information to base any objections. A motion in limine can challenge the reliability of the expert’s testimony or the expert’s qualifications as a whole from an inspection of their credentials.

Also, pre-trial motions are an opportune time to bring up any potential conflicts of interest that may disqualify the opposing expert. For example, imagine an expert has previously worked for or testified on behalf of the plaintiff in another case. For the expert to then testify as a defense witness would be considered a conflict of interest. In these instances, you should first research the opposing expert and their proposed testimony. Next, succinctly draft a written argument to save time down the line at trial. This also avoids reliance on oral, spontaneous objections, which by their nature, will be less informative than a written motion.

Be Alert During Trial

During trial, it is important to object accordingly to any expert testimony that is improper or otherwise irrelevant. As an initial matter, opposing counsel does have the right to conduct a brief voir dire to establish the expert’s qualifications before the jury. This occurs before the expert’s direct examination. The questions will typically focus on educational background, training, or experience. Although a motion in limine may have already touched on the expert’s qualifications, a voir dire can bring out additional information to further support an objection to admissibility.

Once an expert passes the voir dire process and begins their direct examination, it does not mean the testimony is inimitable. Even an otherwise qualified expert may veer into areas that are beyond the permissible scope. This is why it’s important to stay vigilant for potential objections during trial. Such impermissible areas include topics that are not within the expert’s expertise or theories that are not sufficiently reliable. On the other end of the spectrum, an expert, by definition, is not a lay witness or fact witness. Therefore, expert testimony should remain limited to matters where the jury’s understanding requires expert advice.

Lastly, an expert’s testimony (like all witness testimony) needs to be relevant to the facts at issue. In matters of scientific testimony, it is easy to become confused as to what is or is not relevant to the disputed facts. However, timely objecting to irrelevant testimony can save precious trial time while also preventing the expert from appearing more knowledgeable in the eyes of the jury. Attorneys should remember the potential to object on expert testimony begins at disclosure of an expert’s identity. This does not end until the expert is off the stand.


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