The deposition of an opposing party's expert witness can be the single most important deposition in a lawsuit. A successful deposition can have a number of consequential impacts on a case, including setting up a Daubert motion to exclude all (or at least some) of the expert's opinions, and making the party proffering the expert witness rethink the strength (or lack thereof) of the merits of its claim or defense.
So how do you take a successful deposition of an expert witness? Every lawyer will have a different perspective, but in my opinion an effective deposition of an expert witness will attempt to accomplish the following four main goals:
1. Show the expert opinion is not grounded in the facts of your case.
Oftentimes, your adversary will hire a well-regarded, and highly reputable economist whose qualifications on paper are strong. With experts of that caliber, they often are working on many matters and their opinions are not always rooted in the facts of your case. You should carefully review the documents considered by the expert and see if meaningful information in the record was ignored. If so, those can be powerful sources of information to cross examine the expert witness on. You can not only get on the record that the expert did not consider important pieces of the record, but you also can get the expert's likely unprepared testimony on the subject matter of that key information . Even for materials an expert discloses as having considered, perhaps the expert relied heavily on consulting experts and did not study those materials very carefully. Confronting an expert witness with, for example, "bad" documents for the party proffering that expert can often elicit testimony that is conclusory or not credible in the face of the record evidence.
2. Lock in and limit the scope of the expert opinion.
You do not want an expert coming in at trial and offering opinions that were not squarely disclosed in his or her report. One aspect of your deposition should be to get the expert witness on record with clean admissions that he or she is not offering opinions on subject matters not within his or her report. So, for example, if an expert witness is planning to testify about damages, you should lock that expert witness in that none of his or her opinions relates to liability or that liability is assumed in his or her analysis. Turning to the areas the expert witness is opining on, try to narrow the scope of the anticipated testimony or weaken it, if possible. For example, you may be able to limit an expert opinion to certain key assumptions that you can disprove through other witnesses ultimately rendering the expert opinion meaningless or of far less weight.
3. Undermine the credibility of the expert opinions offered.
Another way to attack an expert opinion is to show that it is incredible. One way to do this is to show that the opinions being proffered are inconsistent with prior opinions of the expert. A careful review of articles, testimony, or other public statements by the expert witness is necessary to conduct a line of attack on this basis. Another way to challenge the credibility of an expert opinion is to paint it as extreme or radical. For example, you can test the expert by asking if his or her opinions would hold in other fact patterns (hypothetical or actual ones) that a fact-finder would likely find unpersuasive if the expert steadfastly maintains his or her analysis would not change in those scenarios.
4. See how strongly the expert defends the opinions offered.
Lastly, you should view an expert witness deposition as a chance to see how the expert will present in front of a judge or jury. On the opinions the expert intends to offer, you should conduct a cross examination like you would at trial and see how the expert reacts and defends his or her opinions. Like any other witness in a case, you want to see how the other side's expert will come across to a fact-finder. For example, will they not answer your question, will they seem evasive, do they turn arrogant. Knowing how an expert witness will present in a case, including even if you think they will present well, goes a long way to helping you advise your client on the case.
In order to achieve these four goals and take an effective expert witness deposition, it goes without saying, that ample preparation is necessary. The investment is well worth the time and expense because of the potentially outcome-determinative nature of an expert witness deposition.
Eric S. Hochstadt is a partner at Weil, Gotshal & Manges LLP in New York, New York.