Expert Witness DepositionCountless scholarly articles have been written to address the art of cross-examining expert witnesses during trial. However, less attention has been paid to strategies for cross-examining an expert during a deposition. It is of equal, if not greater import, to have a masterful cross-examination during the deposition of an opposing expert for many reasons. This article enumerates techniques that litigators can use to cross-examine an opposing expert and come closer to their ultimate goals of the litigation.


One reason why the deposition is a critical time for attorneys to weaken the credibility of opposing experts is because it gives attorneys an opportunity to maintain a record of what the expert will testify to at trial. The deposition is often the first (and only) opportunity an attorney has, aside from the trial, to speak to an opposing expert and accomplish several objectives, such as learning the expert’s theories and the bases for those theories, discovering potential weaknesses in the expert’s theories, finding out what kind of effect the expert is likely to have on a jury, and, perhaps most importantly, binding the expert to a certain set of statements. What the expert testifies to during a deposition is what they are bound to testify to at trial, as a deposition is issued under oath and in the presence of witnesses. Accordingly, if an expert were to change testimony, substantially deviate from theories outlined at the deposition, or renege on deposition testimony during trial, opposing counsel’s options are expanded enormously. An expert witness’s inconsistent testimony can not only be used to impeach that witness’s credibility at trial (and potentially have the expert’s testimony, in whole or part, stricken by the court), but if there are blatant contradictions, the expert may face disciplinary measures, ranging from professional discipline from organizational rules from their field that pertain to expert testimony, to perjury charges. It therefore behooves every litigator to heed the strategies herein when cross-examining opposing experts. 

Section One: Be Thorough: The first aspect of a testifying expert’s statement that an attorney should cross-examine is the expert’s theories and basis of those opinions. Specifically, cross-examiners should make the deposed expert be as comprehensive as possible with respect to the expert’s views and the reasons for those views. The reasons for such an approach are numerous and cannot be understated. First, by probing deeply into what the expert is thinking and relying upon when advancing a particular theory, attorneys can figure out whether it would be valuable to challenge the expert’s credibility and reliability under the Daubert, Frye, or other scientific standards for the admissibility of expert testimony. The more attorneys know about exactly what and why an expert believes something to be the case, the more ground to challenge. Often, when witnesses are asked to be thorough in explaining a particular matter, they unwittingly mention irrelevant or unimportant information as a way of bolstering their testimony and making it appear that their theories are undisputed. However, this technique frequently backfires. The best experts will be comprehensive but will not give any more information than is necessary to opposing counsel. But many experts, qualified or not, will volunteer irrelevant information as support for their theories if they feel they are either under attack or on the defensive. Attorneys want this irrelevant and often unimportant information in the record because it offers them more ways to challenge the expert’s testimony at trial. For example, if an expert, feeling pressured to provide myriad sources for a theory, begins to provide sources that are not considered credible within the scientific community, the opposing attorney has gained a valuable piece of ammunition: If the expert had merely relied upon a few reputable sources, the attorney might have been in a difficult position; but once the expert provides even one shaky or weak basis for an opinion, the attorney can use that to make it appear that the expert’s entire opinion is equally lacking in credibility. 

Section Two: Be Specific: In addition to being thorough, attorneys should be very specific when cross-examining a deposed expert. Questions should be asked to uncover each particular theory the expert plans to testify to at trial, as well as to identify each source the expert plans to rely upon. Knowing exactly what studies and authors the expert is preparing to use at trial gives opposing counsel the advantage of being able to locate those studies, as well as the critiques of those studies. This gives the attorney much more credibility at trial, in terms of both whether or not an expert’s testimony should be admitted (according to a judge) and whether it should be considered credible by a jury. An attorney who can cite the specific sources that the opposing expert relied upon and then offer counter-arguments where those studies have been challenged or unproven will be far ahead at trial.

Section Three: Find the Triggers: Another key element of cross-examining a deposed expert witness is to evaluate and determine what that expert’s “triggers” are. In other words, what makes the experts angry? What makes them seem more vulnerable or less credible? What types of questions do they seem at a loss to answer? What types of questions generate discomfort? The deposition gives attorneys for opposing parties the advantage of seeing how an expert performs under pressure before having to actually cross-examine that witness at trial. During this time, attorneys should vary their tone, approach, and demeanor when asking questions, to see what types of questions seem to draw the most emotional responses from the expert. Subsequently, each time an expert appears uncomfortable or shows an atypical demeanor, the attorney should highlight the question asked and answer given, as well as noting what emotional response the expert displayed at the time. Attorneys should be repetitive at times to see if asking questions along similar lines or in certain tones of voice elicit the same or similar emotional reactions from the expert. The expert’s actual ability to perform well in court is largely determined by composure, body language, vocal patterns, and the like. An astute attorney will use the deposition as a training ground to find out what the expert’s verbal and non-verbal weaknesses are and to exploit those at trial.


This article provided an overview of the general strategies attorneys should utilize in cross-examining deposed expert witnesses. Subsequent portions will address more specific techniques and even types of questions attorneys should ask during cross-examination at a deposition. By learning and adopting these tools, litigators will see immediate and immense benefits and gain new ways to cope with opposing expert witnesses at trial.


By: Kat S. Hatziavramidis, Attorney-at-Law