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Frontiers
Has the Jury Decided? What Juries Use to Make Up Their Minds

October 1997

In the normal scope of a trial, one expert may tell the jury that the evidence shows the murderer moved from the kitchen to the murder scene in the dining room. Another witness will say, no, the murderer obviously came in through the living room. And then there are the eyewitnesses, who saw different and contradictory things. How is a jury to decide which witness to believe?

Most jurors take this job seriously and would argue that their verdicts are based only on details relevant to the case. But an ever-growing body of social science research, some of it NSF-funded, is proving what good lawyers know intuitively: Factors other than facts influence jurors' decisions. NSF-sponsored researchers are finding that everything from credentials of expert witnesses to the confidence of eyewitnesses to the comprehensibility of judges' instructions can sway jurors in the courtroom. And, once the juries retire to deliberate, not-so-subtle and not-so-fact-based pressures from fellow jurors force dissenters to switch their positions.

"The work we're funding is telling us a lot about human thought processes and how people handle the information they receive. We're learning about the preconceptions that people bring to court and how evidence and information can be presented to them optimally," says Harmon Hosch, Director of NSF's Law and Social Science Program. "This work has real consequences for people."

The Art of Persuasion

What goes on in courtrooms is really "an exercise in persuasion for the lawyers," says Princeton University's Joel Cooper, who studies attitude formation and change. "What jurors ultimately do is trust one communicator over another."

From persuasion studies in other fields, Cooper knows that people use what psychologists call central and peripheral cues to make decisions. Central cues are the ones pertinent to an argument, the ones that should be used to make fact-based decisions. In ads for cold medicines, for instance, facts about how the medicines work are central cues; peripheral cues might be the attractiveness of persons in the ads.

If the outcome of a persuasion exercise is important to the person receiving the message, she is more likely to use central cues to make her decisions, says Cooper. He hypothesizes that the importance jurors place on making a good decision suggests that they would be more likely to use central cues, but he acknowledges that these ideas have not yet been well studied.

Witness Testimony

In his work on the credibility of expert witnesses, Cooper has found hints that jurors appear to flip between the central and peripheral cues of the testimony. When jurors hear simple, clear testimony from experts, they make their decisions based on the argument presented. But when experts give complicated explanations and use jargon that jurors can't follow, jurors, without realizing it, rely on the expert's credentials to make a decision, says Cooper. Jurors also are more likely to trust experts who testify infrequently and whose testifying fees are modest.

For eyewitnesses, their credibility rests on how confidently they testify, "even though research shows that confidence and accuracy of eyewitnesses are poorly correlated," says Steve Penrod, a University of Nebraska researcher who does NSF-funded work on eyewitness identification. "There is plenty of evidence that [mistaken] eyewitnesses are a major source of erroneous convictions."

Gary Wells, an NSF-funded researcher at Iowa State University, considers such false identifications "the principal cause of the miscarriage of justice." Noting a recent National Institute of Justice study that evaluated cases of prisoners who were released from prison after they were exonerated with DNA evidence, Wells pointed out that, in 24 of the 28 cases studied, people had been wrongly convicted based on faulty eyewitness accounts.

Researchers are steadily acquiring data that demonstrate that false identifications can be easily produced. "If a witness says the suspect had dark, curly hair and only one person in the lineup fits that description, that individual could be falsely identified," says Wells. Because witnesses are more likely to make accurate identifications when they view one person or photo at a time, Wells has suggested that law enforcement personnel present information to witnesses sequentially.

Confidence Factors

Wells also believes that highly confident witnesses who sway juries are inadvertently created by the criminal justice system. Not only do law enforcement professionals influence eyewitnesses' choices by putting certain people in a lineup, Wells speculates that investigators raise witness confidence levels when they tell witnesses that the person they picked out of the lineup is also the person the police consider to be the suspect.

To test his ideas, Wells studied people's sensitivity to reinforcing feedback. His subjects saw a store video that contained images of a person who later killed a store guard. Next, Wells showed his subjects a photo spread of potential suspects. The photo spread did not include a picture of the man in the video. Thus, the subjects all began the study by making a false identification.

To study the effect of feedback, Wells had his testers give one of three feedback options: 1) no comments from the tester, 2) positive feedback from the tester stating they had correctly identified the true suspect, or 3) the news that the suspect was someone else in the spread, thus implying the witness made the wrong choice.

Study participants who had positive feedback reported feeling much greater certainty about their inaccurate choices and a greater willingness to testify in court than did subjects in the two other groups. Wells is now doing studies to see whether eyewitnesses "can be inoculated against such feedback."

Because confident --and possibly wrong -- eyewitnesses have so much power to convince juries, jurors "need to take into consideration the circumstances under which false identifications can occur," says Wells.

The Ultimate Decision

To discover what influences jurors in death penalty cases, William Bowers, of Northeastern University in Boston, and other participants in the Capital Jury Project (CJP) are interviewing jurors who have had to make the critical decision. CJP, which started in 1990 with support from NSF's Law and Social Sciences Program, aims to learn how jurors make their sentencing decisions, that is, how much they're guided by sentencing instructions or subjected to arbitrary influences.

In capital trials, jurors are instructed to consider punishment only after first deciding whether or not a defendant is guilty.

Bowers says nearly half of the jurors questioned in the CJP thought they knew what the defendant's punishment should be before the sentencing stage even began. Forty percent of the jurors said that the type of punishment the defendant might face was discussed during the guilt deliberations of the trial.

"We also learned that many jurors are certain that defendants given a life sentence and not death will be released before the mandatory minimum for parole. The sooner they mistakenly believe the defendant will get out, the more likely they are to vote for death," says Bowers. Holdout jurors, who disagree with the majority, faced psychological pressure from their peers. One juror described how jurors coerced a holdout by making her fearful of losing her job and displaying enlarged photographs of the victim's body.

Also working with funding from NSF's Law and Social Sciences Program, St. Louis University's Richard Wiener studies jurors' legal understanding in capital cases. He finds that jurors, even highly educated ones, don't understand the procedures they are supposed to follow or the legal terms used by judges in their instructions. For example, legally, an aggravating circumstance is one that makes people more worthy of the death sentence, while a mitigating one makes that person less worthy. When Wiener asks jurors to define "aggravating circumstance," he gets explanations like "a circumstance that made the defendant angry."

To make the process easier for jurors, Wiener is studying different ways of giving instructions, including the use of flow charts showing jurors the order they are supposed to follow when evaluating information, and an explanation of common errors that jurors make in interpreting the law.

"The death decision is a complicated one. Jurisdictions differ in the wording and timing of jury instruction. Judges are reluctant to modify those instructions because changes may make it easier for their case to be overturned on appeal," says Wiener. v"But the legal community needs to be more flexible if it wants accurate decisions."

Change comes slowly in the judicial system, as it should, says NSF's Hosch. "We wouldn't want a legal system that responded to every new fad." But as data accumulate, Hosch hopes that jurors and the court system will eventually benefit from the social science research now underway.

 


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