The Inability of Jurors to Self-Diagnose Bias

By Christopher T. Robertson, David Yokum, & Matt Palmer

An adapted extract from the full article, originally published in 96 Denver Law Review 869 (2019).

Whether criminal or civil, litigants are guaranteed the right to an impartial jury. The voir dire process engages jurors in a colloquy to screen panels of potential jurors and remove unduly biased persons. When a juror indicates some feeling or opinion about the litigation, attorneys, facts, or law of the case, the standard practice is to ask the juror if they can set aside that feeling or opinion, and apply the law as instructed.  In short, “can you be fair and impartial”? This is sometimes called “the magic question,” because when a juror reports that he or she can be fair and impartial, then it is highly unlikely that a litigant’s challenge for cause will be successful. We sought to explore whether this colloquy in fact provides useful information to the judge trying to impanel an impartial jury.

A wide variety of biases and prejudices—from racial animus against the plaintiff to professional affiliations with the defendant—might inflict jurors. For any of these biases, the self-diagnosis task that the court asks of jurors can be usefully analyzed as part of a more general process that psychologists call “mental contamination.” Scholars have explained that, to succeed in eradicating such contamination, a person must: (1) be aware that mental contamination exists; (2) be motivated to correct the bias; (3) be aware of the direction and magnitude of the bias; and (4) be able to adjust his or her response.

Consider this process when, for example, a potential juror has been exposed to pretrial publicity (“PTP”) that portrays the defendant negatively based on facts that would be inadmissible at trial. To suppress the biasing influence of this information, the potential juror must first realize the exposure to pretrial publicity has affected his or her judgment, despite a large body of psychological research that people are often ignorant that a bias exists. A step-two failure of motivation would occur if the juror were indifferent about his or her role as a juror, or simply disagreed with the judicial instructions that the impact of pretrial publicity constitutes a bias worthy of eradication. Even if aware and motivated, it is highly unlikely that a juror would have insight into how much bias the PTP exposure caused, a failure of step three; people usually undercompensate or overcompensate for a perceived bias. A failure at the final (fourth) step entails an inability to correct for a bias that is precisely known and unwanted; that is, psychological research suggests some bells cannot be unrung. However, research on the “bias blind spot” indicates that, in general, people are better at diagnosing bias in others than in themselves.

Ultimately, the magic question asks the juror to predict and then accurately report his or her likelihood of accomplishing those tasks. That sort of diagnosis is hard enough, but it’s even harder to diagnose one’s own bias. A juror, despite accurately self-diagnosing that he or she cannot overcome a lingering bias, might nonetheless publicly insist that he or she will act impartially, a phenomenon known as “social desirability” bias. The juror adheres to the social norms of being a good and fair person, that is, of upholding a civic responsibility as any decent citizen would.

Some attorneys or judges may even exploit this effect, “rehabilitating” or browbeating jurors into saying they can be fair, even if this further undermines the real diagnosticity of the colloquy. In short, despite an accurate self-diagnosis of bias, the juror may also earnestly hope that he or she can set aside the lingering bias and serve as a fair and impartial juror.

To test the assumption that juror self-diagnosis is accurate—an empirical claim—we ask whether a juror, whose impartiality has been questioned due to exposure to a potentially biasing factor, can nonetheless decide the case the same as if he or she had never been exposed to the biasing factor. We also test to see whether other-diagnosis, unlike self-diagnosis, might provide a viable voir dire tool, given that people diagnose bias in others better than in themselves.

We implemented this analytic strategy empirically by way of a between-subjects mock jury design on a civil case with two steps: one experimental and one statistical. First, we deliberately biased half of the subjects through exposure to pretrial publicity: subjects in the “control” group read an irrelevant article prior to trial, and subjects in the “treatment” group read an inadmissible article that portrayed the defendant very negatively. Second, we stimulated voir dire screening by asking subjects a series of questions, drawn directly from the U.S. Supreme Court’s guidance, about whether they could be impartial. We then removed from the data set subjects who conceded bias. Those who insisted they were fair and impartial—those who “pass” the magic question screen—are fit for jury duty. If jurors are able to self-diagnose accurately, then the effect of statistically removing those jurors who conceded bias would be to remove the biased verdicts.

Subjects then watched a thirty-two-minute medical malpractice trial video, which include all the key elements of the case, including a judge’s welcome, opening statements, direct and cross of two experts, closing statements, and realistic jury instructions from the judge. After watching the trial, subjects rendered individual judgments, responding “yes” or “no” to whether the plaintiff had proved by the greater weight of the evidence that the defendant committed medical negligence. Finally, subjects who found negligence also awarded noneconomic damages for pain and suffering.