Witnesses make mistakes. And for the adversary, those mistakes can make for useful and entertaining cross-examination. We expect that to occur with fact witnesses who might be naive to the legal process and the attorney's goals, but is there less opportunity to pounce on those mistakes when examining an expert? New research suggests that, in contrast, there might even be greater opportunity. The study (Greene, 2016) finds that subject-area experts are more rather than less likely to make mistakes about their specialty. Indeed, knowing a great deal about a subject doubles the risk of false memories about that subject. As reported in a review in Telegraph, researcher Ciara Greene from University College Dublin, looked at 489 subjects who were measured based on their interest in a number of topics (like politics, science, and sports) as well as their knowledge in those topics. Then they were given a list of four events, three of which were true and one of which was fictional. Having a high level of interest or knowledge in an area increased the chances of true memories, as we would expect, but increased the chances of false memories as well. One fourth of those responding reported a false memory within their area of greatest interest, and those who had significantly greater knowledge on a topic were nearly twice as likely to remember incidents about that topic that never happened. As Ciara Greene noted in LiveScience, "Most people are pretty confident in their own memory for events, but this research shows that false memory is a lot more frequent than many people realize."

Social scientists have long been aware that false memories are common. But why would it be the case that expertise, in the form of greaterknowledge and interest in an area, would correlate with more rather than fewer false memories? The author theorizes that such false-positives are the result of greater familiarity. In other words, new information, whether true or false, has a better chance of feeling familiar to the expert because it relates in some way to something that is already known. As the author told LiveScience, "This can result in a sense of familiarity or recognition of the new material, leading to the conviction that the information has been encountered before and is in fact an existing memory." More knowledge means more possible connections and more possible mistakes. All of that means that experts are prone to error too, possibly more so.

In my experience, many experts take their roles very seriously and prepare extensively even after years of experience. But some experts can take their expertise for granted and end up preparing less than necessary. Fact witnesses, after all, know they are in unfamiliar waters and respond by preparing. Some experts, in contrast, can feel like they have it down and have no particular need to study. And if they shoot from the hip, then they're prone to the kinds of mental mistakes documented in the study.

Of course, there are many checklists on the web which feature questions to ask the adverse expert in deposition. I want to focus on those that might tempt an expert to rely on their broad memory and thus have a relatively greater chance of leading to a mistake or failed recollection. Of course, testimony is not a quiz. But still, thorough questioning can provide a more complete picture and perhaps allow you to uncover a mental mistake or two. So this list may be useful in deposing the adverse expert or in preparing your own witness. These are general areas of questioning, and would need to be phrased to reflect the specifics of the case and the expert's area.

Training and Experience:

  • What educational institutions did you attend during what time frames?
  • What was your thesis or dissertation titles, methods, and conclusions?
  • Have you won any awards or academic honors, prizes, or fellowships?
  • What are the names and dates of past employment?
  • What professional societies currently list you as a member?
  • What licenses or certifications do you hold?

Prior Publications and Testimony:

  • Have you ever taken a position in conflict with your current testimony?
  • Does your report list all publications in the last decade?
  • Are any publications prior to the last ten years germane to your testimony today?
  • Is there anything in these articles that you would now want to change or revise?
  • How would you summarize your past publications?
  • To what extent do you review literature that expresses a position contrary to the position you are taking today?


  • Who made the first contact to retain you in this case, and what did you discuss?
  • What advice or assistance has counsel given you as you completed your work in this case?


  • Did you create a plan for research before you started?
  • What literature did you rely on in creating a method?
  • Can you summarize your method?
  • Has this same method been used successfully in other contexts?
  • Were there any aspects of this method that were abandoned?
  • Are there questions that this method cannot answer?
  • What data are you relying on?
  • Can you summarize the data?
  • What documents or data have you retained or discarded?
  • Was there any data that was not used for this project? If so, why not?


  • Are there any conclusions you explored and then discarded? Or, did you end up confirming every conclusion you set out to?
  • What facts or data would need to be different for these conclusions to be shown to be wrong?
  • How do you respond to critics of these or similar conclusions?
  • Is there any further research that would be necessary to bring these conclusions closer to certainty?
  • What is your own and your field's standard for "reasonable certainty"?