Juror bias is an issue in every trial, civil and criminal alike. Invariably, some jurors arrive in court holding opinions about the parties or the issues in the case. Whether those opinions arise from deeply held prejudices, from life experiences or from exposure to pretrial publicity, they are critical to explore in voir dire.

Unfortunately, courts use an ineffective technique to decide whether a particular panel member’s bias is such that he or she cannot be “fair and impartial.”

We just ask the juror.

When a juror expresses her opinion that corporations put profits ahead of product safety, or her feeling that police don’t arrest people unless they are guilty, she will be asked the following, in some form or fashion:

• Can you put that aside and base your verdict solely on the evidence and the law the court will give you?

• Would any [opinion/feelings/knowledge] you have keep you from being a fair and impartial juror?

Judges rely on jurors’ answers to these and similar questions to rule on challenges for cause. Typically, if a juror vows to try to put an opinion aside and be “fair and impartial” the judge considers the juror “rehabilitated” and will seat him or her.

Does this colloquy, used daily in voir dire and endorsed by appellate courts all the way up to the U.S. Supreme Court, provide the judge and the lawyers with any useful or reliable information?

None at all, according to the finding of a new study that every trial lawyer—and judge—should read.

Jurors’ self-diagnoses provide no useful information for determining bias, the study’s authors concluded. What’s more, they warn that relying on this information may well be the source of wrongful convictions and wrongful civil verdicts.

Strong words, but the data is pretty convincing. Let’s take a look.

Researchers from the University of Arizona used a medical malpractice case – condensed into a 32-minute video—for their tests. First, however, the 174 participants were divided into two groups. One group was given a newspaper article to read that discussed employer incentives for preventive health insurance, a topic irrelevant to the issues in the case. The other group was given an article on the subject of medical malpractice that had been altered to include the defendant physician’s name. The article said he had had prior malpractice claims and settlements and detailed injuries to his patients. In short, those who read the malpractice article were exposed to information damaging to the defense that would not typically be part of a trial.

Then all participants were asked if they had an opinion about the doctor and if so, would that opinion prevent their impartial consideration of the evidence. Most expressed confidence in their ability to be fair, including 87 percent of those who were exposed to the malpractice article and 91 percent of those who read the innocuous article.

All jurors then watched the video and issued individual verdicts.

Jurors who read the prejudicial article were much more likely to find the doctor negligent than those who read the irrelevant article (52 percent as opposed to 35 percent). These results were not surprising to researchers since it is well-established that pretrial publicity can affect verdicts.

Then the data was analyzed after excluding some jurors based on answers to the bias-related questions. Researchers wanted to see if removing those jurors who admitted or even expressed any doubt about their ability to be impartial would diminish the effect of the adverse pretrial publicity.

Screening out those jurors made no difference at all.

Before screening, 52 percent of the group exposed to the negative publicity found the doctor liable. One might expect that taking out those jurors who had expressed possible bias would lower that number. Instead, the percentage slightly increased to 53 percent of the group finding against the defendant.

Relying on jurors’ own assessments of their ability to be impartial did absolutely nothing to reduce the biasing effects of pretrial publicity. Why?

Obviously, it’s difficult to admit an inability or unwillingness to be fair. It’s much easier—and socially acceptable—to vow to do one’s best to overcome any partiality or to be overly optimistic about one’s ability.

The much bigger problem, however, is that most jurors don’t recognize that they have any bias in the first place. Simply put, they can’t diagnose themselves. Yet time and again judges rely on jurors’ self-assessments to deny motions to strike for cause.

The authors of this study make a radical suggestion: Courts might use the same standard to disqualify jurors that is commonly used to recuse judges. Judges are told they should recuse themselves whenever their impartiality might reasonably be questioned. Applying that to jurors would mean if a juror has been exposed to prejudicial information or expressed an opinion at all on the relevant issues, he or she should be dismissed from the pool.

The authors also suggest types of voir dire questions that may help jurors be a bit more objective. For instance, try asking jurors to imagine not having read that damaging newspaper article or not having had that bad experience with police. Would they then have a different outlook on the case? Or ask the juror if he or she believes that someone else who holds a similar opinion or has had a similar experience might have difficulty being impartial.

While more voir dire may assist in making decisions on juror qualification, the bottom line is this: self-diagnosis of bias simply doesn’t work. Don’t rely on it.

The article by Robertson, Yokum and Palmer, “The Inability of Jurors to Self-Diagnose Bias,” Arizona Legal Studies Discussion Paper No. 12-35, April 24, 2013, can be found here: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2109894.