Five Practical Rules for Excluding an Opposing Party’s Expert

While excluding expert testimony can be a difficult task, you should always be prepared to do so whenever possible. This article identifies five practical rules to help increase your chances of excluding an opposing party's expert.

1. Know the Law

The first and most important rule to excluding an expert opinion is to know and understand the law. Federal Rule of Evidence 702, which generally has been adopted by most states, provides that an expert witness may testify to an opinion if four prongs are met.

The first prong essentially requires that the opinion be relevant to the case at hand. While important, this prong is not frequently relied on to exclude expert opinions. The second prong requires that the opinion be based on “sufficient facts or data.” While this prong is frequently relied on to exclude expert testimony, it does not necessarily depend on a Daubert analysis. Rather, this prong is often challenged when experts either mischaracterize, misapply, or make improper assumptions about important facts that they relied on in forming the basis of an opinion. An example of this is an expert who has mischaracterized prior testimony or has mistakenly assumed critical facts not yet in evidence.

More notably, however, the third and fourth prongs are the requirements addressed in Daubert and most subsequent caselaw. These prongs require expert testimony to be “the product of reliable principles and methods,” and for the expert to have “reliably applied the principles and methods to the facts of the case.” More simply, these prongs concern the “methodology” used by experts in forming their opinions.

Specifically, the Supreme Court in Daubert set forth a non-exhaustive list of factors that the trial court should consider in determining the sufficiency of an expert's methodology, including:

• whether the expert's theory can be and has been tested;• whether the theory has been subjected to peer review and publication;• the known or potential error rate of the technique; and• whether the technique is generally accepted in the scientific community.

While Daubert is the seminal case in most jurisdictions for excluding an expert opinion, it is critical that you promptly familiarize yourself with any analogous decisions that would also apply to your case.

2. Be Diligent, but Act Fast!

Like any important witness, it is critical that you adequately prepare for the deposition of an opposing expert. This means that, prior to the deposition, you have filed expert interrogatories and performed an independent investigation, including a review of the expert's prior opinions, testimony, and publications, as well as any Daubert challenges made against him or her.

Additionally, it is important that you timely file a targeted subpoena duces tecum with your deposition notice. Among other things, your subpoena duces tecum should request the expert to produce all records that he or she relied on in forming his or her opinions, as well as all non-privileged expert/forensic reports that the expert has previously prepared―directly related to your case or not.

However, keep in mind that many trial orders only provide you with a limited amount of time between the expert disclosure date and trial. Thus, it is crucial that you promptly request, coordinate, and notice the deposition of an opposing party's expert, ensuring that you have enough time to take the deposition, order the transcript, file your motion, and have it heard well in advance of trial. Generally, the closer to trial the motion is argued, the less likely the court is going to grant it.

3. Ask Targeted Questions at the Expert's Deposition

While there are other considerations when deposing an expert—mainly to elicit impeachment and other cross-examination material—if you reasonably expect to exclude an expert, you must make the appropriate inquiry at his or her deposition. To do this, you should incorporate the respective law and legal terminology into your examination.

First, you must make sure the opposing expert identifies every opinion that he or she is making with respect to the case. Next, you will need to elicit the factual basis that he or she has relied on in forming each of these opinions (a.k.a., the extrinsic evidence provided to or otherwise obtained by the expert). Then, you must have the expert identify and describe in detail his or her methodology, as well as the specific application of this methodology, that he or she used to arrive at each of his or her opinions. Pursuant to Daubert, ask the expert whether each methodology has been tested, is subject to peer review, has a known or potential rate of error, and is generally accepted within its respective scientific, medical, or professional communities. When doing this, be sure to make a specific inquiry into the basis supporting the expert's testimony concerning each of these factors.

Often, opposing experts will rely entirely on their “experience” as the basis for their methodologies. While this does not per se make an expert opinion inadmissible, it certainly strengthens your argument to exclude such testimony. Additionally, every time an expert gives an opinion, make sure you ask whether he or she is able to make this opinion to a reasonable degree of scientific, medical, or professional certainty. If the expert admits that he or she cannot do so, or otherwise evades such question, there is arguably no greater evidence that his or her opinion is improper and should be excluded at trial.

4. “Lock In” The Expert's Testimony Whenever Possible

At some point, every attorney reads a deposition transcript and wishes that he or she would have cleared up a particular exchange. Much like impeaching a witness at trial, you will need to “lock” experts into their testimony if you want to rely on it to exclude their opinions. To do so, you must ensure that both the questions and answers within a testimonial exchange are clear and definite. While seasoned experts may make this difficult for you, do your best to tailor your questions narrowly and to confront any non-responsive or evasive answers consistently. If you do not lock in the expert's testimony, opposing counsel will surely point to other testimony, evidence, or even supporting affidavits to rebut your motion. Generally, a good rule is to elicit as much information as possible from the experts before challenging them with any confrontational inquiries.

Also, every time an expert did not do or consider something important with respect to his or her opinion, you should aggressively flesh this out. Get the expert to provide you with a series of “Nos” that you can easily use to bolster your motion. This is often called “accentuating the negative,” and if done correctly, can be an effective way to discredit an expert opinion.

Finally, if the expert has prepared a report, use it to your advantage. While these reports are usually inadmissible to bolster an expert's opinions, it can certainly be used at deposition to lock in his or her testimony.

5. Keep Your Audience in Mind

Ultimately, to exclude an expert opinion, the only person you need to convince is the judge. While there are several considerations needed to accomplish this, here are a few important ones to keep in mind.

Make sure to structure your written motion in a way that it can be easily read. If you are making multiple arguments for why the expert's opinions should be excluded, organize them into separate sections and spend the time to title them accordingly.

Do your best to eliminate any unnecessary facts, arguments, or citations. While it is tempting to regurgitate every bad aspect of an expert's testimony, chances are that much of this information goes to the weight of the opinion―not its admissibility. There is a good chance that the judge may only have time to read your motion once before it is heard, so make every word count. Generally, if you do not intend on referencing information at oral arguments, it is probably best to omit it from your written motion.

If there is an expert report, feel free to cite it interchangeably with the expert's testimony. If there is any ambiguity between the expert's testimony and report, cite whichever one you believe will better support your arguments and let opposing counsel explain the inconsistency.

Keep in mind that your goal at oral arguments is still the same: to convince the judge to exclude the opposing expert's opinion. The best and most effective way to do this is to reinforce your written motion emphatically. Your goal is not to impress the court with your public speaking skills or ability to flatter.

While it is important to anticipate and rebut any counterarguments from opposing counsel, do not do so at the expense of your motion. Make sure you clearly state your arguments and supporting evidence before you start tearing down the plaintiff's rebuttal. Ultimately, you want to make your arguments to the court as fluid as possible.

Finally, because the burden ultimately falls on the plaintiff to prove his or her expert's admissibility by a preponderance of the evidence, your oral argument is your best opportunity to emphasize this to the court. Too many attorneys shoot themselves in the foot by arguing these motions as if they are moving for summary judgment, which is a substantially different and higher standard.