On Thursday in a North Carolina courtroom, 12 of John Edwards’s peers failed to reach a verdict on five charges against the former senator and vice presidential candidate, and declared him not guilty on another. “Thank goodness we live in a country that has the kind of system that we have,” Edwards said afterward on the courthouse steps.
But would a system with fewer jurors have been able to agree on his guilt or innocence?
“Defendants often think that larger juries entail a greater protection by increasing the probability that a dissenting juror could ‘hang’ the jury,” economists Barbara Luppi and Francesco Parisi write in “Jury Size and the Hung-Jury Paradox,” a recent paper from the University of Minnesota Law School. “However, evidence suggests that changes in jury size have not had much impact on the probability of hung juries and conviction rates.”
According to the authors, the number of mistrials has not changed much since a 1970 Supreme Court decision reduced the number of required jurors from 12 to six. This goes against not only probability theory but intuition. Isn’t it easier to convince fewer people than a crowd? Not necessarily, since what Luppi and Parisi call “informational cascades” shape jurors’ decisions.
“When jurors have little information on a subject, they are more likely to make up their minds on the basis of what others believe,” they explain. “The process of jury deliberation may create consensus, but at the same time it may amplify the errors of some jurors and lead to wrong deliberations.”
The result? A “hung-jury paradox” that means “unanimity can be reached just as easily in a jury of twelve as in a jury of six.”
Of course, size isn’t the only factor that determines whether a jury will reach a verdict. Edwards’s jury, for example, was racially and economically diverse, and included a retired railroad engineer and a corporate vice president. Such disparate backgrounds, the authors argue, can affect juries in different ways — sometimes leading to a “convergence of views,” sometimes preventing consensus.
“The wrong belief of one juror could spread within his subgroup and lead to a hang jury,” Luppi and Parisi write. “Highly heterogenous juries should be kept small and very large juries should be kept mildly heterogeneous, to avoid the formation of clusters of dissenting jurors.”