When thinking about the title for this post, I came awfully close to saying that certainty “matters more” than accuracy, but I thought that perhaps it might sound too cynical. But that stronger version is supported by the research: Jurors do seem to pay more attention to witness certainty than to any other witness characteristic, and certainty bolsters credibility even when there are reasons to doubt the accuracy of the testimony.

One recent study on eyewitness testimony (Key, et al., 2022) bolsters that conclusion. Looking at what creates credibility for criminal eyewitness testimony, the team of psychologists found that the most important factor was how much certainty the testifying witness claimed to have over the identification. This primary emphasis on in-court certainty meant that some testimony was more likely to be believed even when there were reasons to doubt the accuracy of the testimony. In other words, the research underscored the problem with eyewitness testimony: “jurors favored high confidence in cases where they should not.” The current study is in line with previous research showing that, of all variables associated with an eyewitness, certainty remains the best, and in some cases, the only reliable predictor of whether jurors will believe the testimony. In this post, I will look at the reasons why, and what this says to the typical witness.

The Research: Certainty Is the Most Important Witness Quality

The research team asked 522 participants to review a trial transcript in a robbery case involving an eyewitness identification. They varied the degree of certainty expressed by the witness, both at the time of initial identification as well as their certainty in the courtroom. In the process, they could look at certainty that either degraded or inflated over time – either of which should give a juror cause to question the reliability of the identification. They found, however, that high confidence in the courtroom tended to trump those concerns. The researchers call this “the confidence heuristic,” or the notion that witness confidence is used as a shortcut in assessing reliability – if the witness is certain, the information is true. That heuristic tended to override the inconsistency of an assessment that varied over time. They conclude, “courtroom confidence, if available, may be difficult to ignore.”

The researchers see this as a negative – the article title is “High eyewitness confidence is always compelling: that’s a problem.” They see the confidence heuristic as being one of the reasons that flawed eyewitness testimony is often “unduly persuasive” in a way that fuels false convictions. That is obviously an important concern. But I think the research also has something to say to all witnesses and not just those who feel they are witnessing a crime. Chances are good the mental shortcut that we apply in equating certainty with accuracy applies in other contexts as well. So when testifying, I think it makes sense to be thoughtful about one’s certainty – both actual certainty and expressed certainty.

The Recommendations: Don’t Artificially Downgrade Your Certainty 

Imagine a witness on the stand when being asked the key question of the case: If she hesitates, looks at her attorney, precedes the answer with some qualifiers (I think… to the best of my recollection…I will say…) and then diminishes it afterwards (…at least that is what I remember) it isn’t going to have the punch of a simple, clear, and definitive statement. I see four important considerations for certainty in testimony.

Don’t Create a False Certainty

A witness should only be as certain as their recollection and judgment can support – no more, but also no less. Not only is it unethical to exaggerate certainty (that should be enough) but it can also be a recipe for being burnt during a good cross-examination. Rather than seeing the research as an inducement to false certainty, I would rather see it as a call for not allowing factors in the situation to artificially degrade the real certainty that a witness has or should have.

Don’t Generalize Your Uncertainty

Often, cases center on events that happened years ago. No witness remembers everything that happened. But those elements of realistic uncertainty should not diminish the things the witness actually is certain about. For example, you may not remember what you actually said or did, but based on knowledge of your own common practice and your own judgment, and about what you would have done, you can still be certain in your answer. Witnesses should do a careful audit of what they are and are not certain about.

Don’t Let Situational Uncertainty Become Substantive Uncertainty

It is common for witnesses to be uncertain about the legal process and not sure about exactly how deposition or trial testimony is supposed to go. Particularly for fact-witnesses with little to no prior experience in the witness chair, it can be daunting. But that uncertainty over the process should not bleed into uncertainty about the substance of the testimony. Practice with counsel should familiarize the witness with the norms and expectations, while still preserving the ability to be certain about what the witness knows, did, saw, and believes.

Don’t Let Your Politeness Get in the Way

For some witnesses — and there is often a cultural component to this – being too assertive or too sure of oneself can feel rude. It is also sometimes the case that when people feel themselves to be in a lower-power position, they will dial down the certainty of their own speech. When hesitant speakers in a meeting use words like, “I don’t really know, but…” or “This is just a thought…” they are employing what are called “softeners” as a communication strategy to avoid perceived offense. That can be a good idea in a tense meeting or a negotiation, but it is generally a bad idea for testimony. Don’t create the appearance of uncertainty just as a way of being polite.

Often I tell witnesses, the jury doesn’t have the ability to see you work, or to see the facts from your perspective. They can’t go back in time to the scene with you to see what you saw. So all they have to work with is your communication. Your certainty is a big part of what they will take away, so don’t do anything to unrealistically undercut that certainty.

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Key, K. N., Neuschatz, J. S., Gronlund, S. D., Deloach, D., Wetmore, S. A., McAdoo, R. M., & McCollum, D. (2022). High eyewitness confidence is always compelling: that’sa problem. Psychology, Crime & Law, 1-22.

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