I recently received a jury-duty letter, a notice that inspired me to learn everything I could about the science of jury selection. I could say this was because I’m naturally inquisitive, but the truth is I’m a bad citizen who wanted to get out of jury duty. I was hunting for tell-tale signs of bad jurors so I’d know exactly how to act during jury selection to ensure no one would want me meting out justice anytime soon.

I expected to find a wealth of information. After all, since the famous 1972 “Harrisburg Seven” trial, in which sociologists helped defense attorneys pick a jury that would go on to acquit their clients of plotting to kidnap Henry Kissinger, more and more legal teams have used social-science expertise during voir dire. Today the American Society of Trial Consultants boasts roughly 400 members, and “it’s gotten to the point where if you don’t hire one as a big attorney, you could be sued for incompetence,” says Franklin Strier, law professor at California State University, Dominguez Hills and author of Reconstructing Justice: An Agenda for Trial Reform.

Thanks to the well-publicized roles of jury-selection experts in headline-grabbing cases such as the O.J. Simpson trial, the first Rodney King trial, and the $2.9 million “hot coffee” lawsuit against McDonald’s, scientific jury stacking has also attracted public interest, not to mention trepidation. For many people, there’s something disconcerting about an expert being able to calculate how they’re going to decide a case based on their gender, background, and other characteristics.

With all the money and attention focused on scientific jury selection, I figured I’d find a lot of clear-cut evidence about how different types of jurors tend to act. But as it turns out, the inner workings of the jury box are nearly as mysterious as ever. As Neil Kressel, psychology professor at William Patterson University and author of Stack and Sway: The New Science of Jury Consulting, told me, “The preponderance of academic researchers agree it is extremely difficult to figure out how a jury is going to decide.”

Despite hundreds of studies on the matter, ranging from simulated trials to post-trial juror interviews to field studies of real juries, most obvious juror characteristics, including occupation, income, religion, and age, haven’t been shown to correlate in any consistent way with verdict outcomes. Personality types aren’t much more instructive. People who believe “in a just world,” for example, have been known to come down hard on criminal defendants in some cases, while at other times they seem to lack sympathy for the victims of the crime.

The jury box turns out to be a lousy laboratory for the study of human behavior. For one thing, it’s not a juror who decides the fate of a case, it’s a jury. Even if an individual were predisposed to a certain verdict, that doesn’t mean that verdict is going to stick during deliberations with fellow jurors. To truly understand how group dynamics play out leading up to a verdict, researchers would need access to jury deliberations, and that’s strictly off-limits in real trials.

There are other complicating factors at work. It’s hard, if not impossible, to separate out the impact of juror characteristics on a trial outcome from all the other variables at work in a case. For example, those who are able to afford trial consultants trained in the science of jury selection can also pay for the best attorneys, so it’s hard to know which is responsible for a successful verdict. Even in the Harrisburg Seven trial—where defense attorneys were thought to have gotten an edge by getting rid of jurors who were religious, conservative, and pro-government—the verdict might have gone in their favor because the prosecution had a weak case to begin with.

There’s a final hitch with scientific jury selection. Even if experts were able to determine the best possible mix of jurors for a given case, there would be no way to ensure that the desired mix ends up in the jury box. Lawyers don’t select jurors during voir dire; they eliminate them—and they’re restricted in that regard, too. While the defense and prosecution can challenge an unlimited number of jurors if there’s clear proof of bias, each side is only allowed a handful of peremptory challenges, the rejection of jurors without a reason. “You have only got a few slots to play with,” says Kressel. “And you can’t choose who the replacements are going to be, so the next person in line could be worse.”

Even with all these complicating factors and fuzzy science, however, a few juror traits have been quantifiably associated with verdict outcomes. Unfortunately, those correlations are among the most troubling imaginable for our legal system. Dennis Devine, a psychology professor at Purdue University, combed through the research for his upcoming book, Jury Decision Making: The State of the Science, and found that jurors tend to be more lenient on defendants who share the same race. The impact is fairly minor—that is, except in capital cases, in which black defendants are significantly more likely to receive the death penalty when there are a lot of white men on a jury and no black men to offset them. The trend has been traced through hundreds of death-penalty trials, not to mention corroborated by lab experiments, and the bias is worse if the black defendant is accused of killing a white person. Devine believes such discrimination is most noticeable during capital cases because of the unique nature of death-penalty verdicts. “A decision about who should live and who should die is inherently more subjective than whether someone killed somebody or not,” he says. “It is therefore more susceptible to our implicit racial biases.”

Findings like that leave the unregulated and certification-devoid jury-selection industry in a bit of a bind when it comes to touting its own efficacy. On one hand, jury-selection experts would do well to showcase their success, both to increase business and encourage further research on the matter. On the other hand, they don’t want to boast at being able to violate people’s rights to an impartial jury. As Strier tells me, “It’s either expensive or a waste of time if it’s ineffective, or if it is effective, then it is unfair.”

This catch-22 may be one of the reasons Philip Anthony, CEO of one of the country’s largest and oldest trial-consulting firms, is less than effusive about scientific jury selection’s effectiveness. “What we’ve found historically is there isn’t one overwhelming pattern you can apply across different cases,” he tells me. Instead, says Anthony, “we collect data from enough surrogate jurors in advance of trial that we can then look at patterns in the data at a statistical level, to see what sort of characteristics, behaviors and attitudes correlate with verdict preference in a case.”* He’s also quick to point out that firms like his do a lot more than just focus on voir dire; they also help clients prepare arguments, witnesses, and evidence, for example.”We do our best to apply rigorous social-science processes to studying the data, but at the end of the day, you only know so much about the people in the jury box,” says Anthony. “There is as much an art component as there is a science component.”

Since even the practitioners of scientific jury selection are reluctant to emphasize the science of what they do, some folks think it’s time to get rid of the business altogether. One way to do so would be to do away with peremptory challenges, as England did in 1988. If lawyers aren’t allowed to remove jurors at will, there’d be no need for them to consult with jury-selection experts. Sure enough, the English legal system appears to be largely unfamiliar with scientific jury selection.

Then again, such drastic measures might not be necessary. The jury-selection business is facing hard enough times as it is. When I arrived at the courthouse the day of my jury duty, ready to use my list of bad-juror characteristics and botch my way through voir dire, I never even made it into the courtroom. The case had gone away, I’d been told, and likely settled out of court. That’s the trend: With the vast majority of criminal cases now settled by plea bargains (last year, 97 percent of all federal criminal convictions came from guilty or no-contest pleas, up from 86 percent in 1990) and an increasing number of civil cases going to arbitration, most legal matters never reach trial. Pretty soon, there might not be any juries left to stack.

Tips from jury-selection experts on how to get out of jury duty

So you’ve been called up for jury duty, but you really don’t want to serve. Are there certain ways you should act during jury selection that will surely get you booted? The short answer is no, since jury-selection experts haven’t had much success generalizing about what makes a good juror versus what makes a bad one. But according to jury-selection researchers and trial consultants, there are a few things you could do that might set off warning bells:

Be verbal. If you want out, jury selection is not the time to hold your peace. As Purdue University psychology professor Dennis Devine says, “The ones who don’t say anything and fall through the cracks are the ones more likely to stay.”

Be subtle. On the other hand, don’t ham it up. If you’re too blatant in your attempts to get off the jury, the judge may keep you out of spite, warns William Patterson University psychology professor Neil Kressel. In other words, don’t dress up like a Princess Leia hologram.

Be biased. Once you’ve listened to the description of the case, raise your hand and say you can’t be fair and impartial about the matter at hand. The judge will probably bark at you, warns Philip Anthony, CEO of the trial consulting firm DecisionQuest, but if you stand your ground, they will have to let you go.

Correction, Feb. 27, 2012: The original version left out part of the quote and in so doing misrepresented Philip Anthony’s views on the value of scientific jury selection. (Return to the corrected sentence.)