Cross-examining an expert at trial can be very challenging. The expert will almost always have more substantive knowledge of the topic they are testifying about than the questioning attorney, and will often be a professional witness. Here we provide our top ten tips for destroying an expert witness during cross-examination at trial:
- Consider your tone. You will want to carefully consider the tone that you take when you begin your cross-examination. If the witness and their counsel have already built up a rapport and some amount of trust with the jury—and particularly if the jury has not yet had an opportunity to get to know you—a jury may not appreciate you immediately taking an aggressive or indignant tone with the expert. While a jury may be less likely to feel connected to an expert witness than they are to a fact witness, you should still consider whether the expert had a particularly likable demeanor, such that you will need to earn the jury’s trust during cross examination before building up to more aggressive questioning.
- Limit questions to yes or no questions. An expert will almost always be more experienced and comfortable in the subject matter than you are, and may be able to avoid providing clear answers to open-ended questions, or may use terms of art or language that can be difficult to understand, or ask follow up questions about. Open-ended questions may also provide an expert with an opportunity to put his or her expertise on display for the jury. So it is often to your advantage to ask questions in a form that will limit the expert to a “yes” or “no” response. And limit each question to eliciting a single point from the witness. Even with perfectly worded questions, an expert will likely try to avoid answering with a simple “yes” or “no” so it will be critical to maintain tight control of the witness and call the witness out when he or she is not answering the question asked.
- Focus on 2-3 key issues. You need not cross examine the expert on all areas of their opinions. Instead, you may want to limit your questioning to a few key areas in which the expert is factually mistaken, ill-prepared, or lacks credibility. You can more effectively undercut the expert’s credibility by focusing on a few issues where the witness is truly weak, rather than attempting to attack all of their opinions with less persuasive angles. And this has the added benefit of keeping jurors from becoming bored and inattentive through a lengthy, technical examination.
- Develop a theory. Consider the story you want to tell with your cross examination. Is your theory that the expert is a hired gun who will say anything for his or her client? Or that the expert based their opinions on a fundamental misunderstanding of the facts? You should craft your questioning to tell your story to the jury through a progression of short and simple questions.
- Lock the expert into “value propositions.” At the beginning of the examination, it can be helpful to lock the expert into certain “value propositions.” For example, questions like “You approached this assignment in an unbiased manner, without any preconceived notions, right?” “You did not ignore evidence that was unfavorable to your client?” Then when it comes time to question the witness on the substance of his or her report, you can identify for the jury instances where the expert violated those value propositions—such as where the expert did not consider documents or testimony from the opposing party which undermined the expert’s opinions.
- Highlight any unreasonable assumptions made by the expert. One potential ripe area for cross examination is the assumptions that an expert made. It is common, and often necessary, for an expert to make assumptions in order to complete his or her analysis. The expert must often work with imperfect or incomplete information. You may want to highlight for the jury if any assumptions that were inconsistent with the facts or academic literature in the field. You may want to highlight any assumptions that were unreasonable or did not make common sense. It is also important in your questioning to highlight the impact of any such unsupported or unreasonable assumptions on the outcome. If you can demonstrate to the jury that the assumptions are unreasonable or inaccurate, then you may be able persuade the jury that the ultimate conclusions are not credible or reliable either.
- Call out work the expert did not perform. Another area ripe for cross examination are all the analyses that the expert did not perform. It may not even be necessary to ask if additional tests or analyses, or review of additional documents may have caused them to change their conclusions. If you are able to bring out enough tests or analyses that the expert did not bother to conduct, you may be able to convince the jury that the expert did a shoddy analysis.
- Call out work completed but omitted from the expert report. In addition to cross examining on work the expert did not perform, you may also wish to question the expert on work he or she did perform, but omitted from the report. Many sophisticated testifying experts will be careful to have their staff shield them from any unfavorable analyses that they do not wish to include in their report. Nevertheless, in some (New Austin Office and Partner Hires continued from cover) circumstances you may be able to identify particular analyses that they performed, but abandoned because the results were not beneficial to their client. This line of questioning could have the benefit of both revealing analyses that are beneficial to your client, while also making the opposing expert appear untrustworthy before the jury.
- Highlight sources not considered by the expert. Another potential area for cross-examination are sources that the expert chose not to consider. These sources can include treatises and other reference materials, as well as evidence in the case. As to the former, at deposition, ask questions about what materials they view as reliable in their field. For example, what books or articles do they use to each their courses? What books do they look to themselves when doing research in their field? Then if you are able to identify something in those materials that is inconsistent with the expert’s opinions, you can admit the material under FRE 803(18) (Statements in Learned Treatises, Periodicals, or Pamphlets). On cross-examination at trial, remind the expert that they had testified that the material at issue was reliable, and then read the selection into the record, closing by asking if you read the statement correctly. You do not need to ask the expert if they agree with the quoted statement— opposing counsel can do so on redirect. Similarly, as to evidence, you may be able to establish that the expert reviewed only documents or deposition testimony from their own client, or did not review some particular categories of documents or data you believe to be significant. If they did not even review the materials, they cannot reliably say whether those materials could have had an impact on their conclusions.
- Establish bias. After laying the groundwork at deposition, you may also be able to persuade the jury that the expert is biased and therefore unreliable. Have they exclusively represented clients on one side of the “V”? How much is he or she paid per hour? You may point out how many times the defendant’s class certification expert has submitted a report on class certification, and the fact that he or she has never opined that a class should be certified. You may point out that the antitrust defendant’s economic expert has submitted reports in 35 antitrust cases, but never opined that a defendant’s conduct was anticompetitive. You may learn that the expert has a history of testifying on behalf of the opposing party, or having research funded by that party. All of these facts can undermine the expert’s credibility in the jury’s eyes.
In addition to applying these ten principles, the key to a successful cross is ensuring that the jury understands the significance of the points elicited on cross. Whenever possible, you want the jury to understand the point of your cross-examination by the time the cross examination is completed. Although there is certainly an opportunity to bring the points together in a closing argument, many jurors will have already made up their minds by the time you get to closing arguments. At the conclusion of a good cross examination, the jury should understand the significance of each “admission” obtained during the examination, and their impact on the larger case.