By Dr. Ken Broda Bahm –
Attorneys, consultants, and experts know testimony needs to be delivered with more than just clarity and authority. It needs confidence. Jurors and judges alike are more comfortable with an expert’s testimony when it is delivered with self-assurance and conveyed with certainty. But according to research sponsored by The American Society of Trial Consultants, the advantage of greater confidence is true only up to a point. As profiled in Psychiatric News, the study (Cramer, Brodsky, & DeCoster, 2009), tested the effectiveness of experts at three levels of perceived confidence: high, medium, and low. The conclusion is when it comes to witness confidence, more is not always better, and those who showed a medium level of confidence ended up having the highest credibility. This post takes a closer look at this research and provides a few practical guidelines on ways that experts can demonstrate appropriate confidence without going too far.
The study used a death penalty case as an example, and specifically looked at the credibility of the prosecutor’s expert testimony on a convicted murderer’s likelihood of committing violent acts in the future.
Understanding the impact of this study comes down to appreciating the differences between the three levels of confidence that the researchers tested. In the “low confidence” condition, each of two actor/witnesses testified while using varying pace, a quavering voice, corrections, and frequent use of “you know.” Those in the “medium confidence” employed a moderate and stable voice, smooth narrative statements, and acknowledged “reasonable certainty.” Finally, “high confidence” witnesses used a loud and strong tone of voice, spoke rapidly, and made absolute statements using “always,” “all,” and “I am certain.” Comparing the credibility ratings provided by the 299 research participants, the results summarized in Psychiatric News looked like the chart below.
While the researchers did a check to make sure the more confident versions were indeed perceived as more confident, it seems likely they were measuring something else as well, namely unwarranted certainty. Those in the highest confidence conditions made frequent “I am certain…” statements about a murderer’s likelihood of committing future violent acts. Study participants could have easily felt this is something no human, expert or otherwise, could ever be certain about.
For that reason, the study should not be interpreted as providing expert witnesses with the blanket advice to moderate their confidence levels. Rather, it suggests experts should keep a careful accounting of what they should and shouldn’t be certain about. For example, here is what I’d suggest goes in each category, based not only on research, but on my own experience as well.
Be certain about:
- Your qualifications You should be unambiguous about your ability to provide expertise, or you should not be testifying.
- Your work The efforts that support your opinion — review, analysis, survey, or experiment — should be something you can defend in unwavering terms
- Your conclusions Ultimately, you should be sure of your opinion, which does not mean exaggerating the strength of your conclusions. Importantly, remember even a conclusion about a probability or an estimate can be stated in certain terms (e.g., I’m absolutely certain that the chances of “heads” on a coin flip is approximately 50 percent).
- Your comparative advantage Most often, you are responsible not only for supporting your conclusions, but for undermining the conclusions of opposing experts as well. So be definite about both the “I’m right” as well as the “They’re wrong.”
But don’t be certain about:
- The unknowable As the study shows, if a conclusion is suited to probabilities or estimates, but not to certainties, you protect your credibility be leaving a bit of breathing room around your opinions.
- The case outside your scope The quickest way for an expert to lose the aura of authority is to appear to have opinions on those aspects of the case that are best left to the lawyers and other witnesses.
- The implications Your testimony is your testimony, but what a jury does with it is their business. Your judge will not let you dictate to themselves or the jury, but you shouldn’t even seem to be telling them what to do. Your testimony should provide a clear path on the issue, but don’t sacrifice your credibility by appearing to be just another advocate. Teach, guide, but don’t direct.
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Related Posts:
- Expert Witnesses: When Criticized, Don’t Just Respond, Riposte!
- When Crossing or Responding to Your Opposing Expert Witness, Look for the L.I.E. (Large Internal Error)
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Cramer RJ, Brodsky SL, & DeCoster J (2009). Expert witness confidence and juror personality: their impact on credibility and persuasion in the courtroom. The journal of the American Academy of Psychiatry and the Law, 37(1), 63-74 PMID: 19297636
Photo Credit: zhurnaly, Flickr Creative Commons