Trial Juries, No. 12

A trial jury is a select number of individuals that is chosen to represent the diverse views of an unbiased community. Jurors serve a very important function within the justice system. The jury must determine whether a defendant committed the crime charged in a criminal case or whether the defendant injured the plaintiff in a civil case. Historically, juries consisted of twelve people. However, today the norm is six-to-twelve people.

Where did the number twelve come from? And why did we stray form it?

The number twelve is actually linked to the biblical notions of Jesus and his Twelve Apostles, similar to a judge and his or her twelve jurors. The use of twelve jurors was the common practice throughout six centuries of world history. The United States followed history and tradition and unquestionably stood by the use of twelve person juries in all jury trials—federal and state, criminal and civil—up into 1970 when this practice was challenged in Williams v. Florida. In Williams, the Supreme Court held that a six-person, state court, criminal jury was constitutional. The Court found that twelve person juries were a “historical accident” and “unnecessary to effect the purposes of the jury system.” Thus, the Court held that smaller juries that provide the same function as twelve-person juries are constitutional. Social scientists largely disagree with this opinion for numerous reasons.

So, what size jury ensures proper deliberation?

The astounding answer is twelve. Studies show that smaller juries do not provide the same function as twelve-person juries. For starters, smaller juries are less representative of the community. These juries are less likely to include members of racial minorities. The decreased diversity and inaccurate community representation negatively impacts jury deliberations greatly. This is because a full range of community perspectives cannot be achieved in deliberations with smaller juries. Further, smaller juries lead to less predictable outcomes. The predictability of larger juries is rooted in their ability to recall the evidence more accurately, thus allowing the jury to rely more on the probative evidence derived from the trial rather than conclusory statements. In contrast, the unpredictability of smaller juries results from fewer viewpoints impacting the group dynamic. This leads to a lower quality of jury deliberations. For example, within smaller juries, a single juror has greater weight to pull the other jurors toward a more outlier point of view causing unpredictability.

Very few studies over the last 50 years show favorable data for smaller juries. In fact, there is contradictory findings about the cost-effectiveness of smaller juries. Cost seems to be the main drive behind upsetting the traditional twelve-person jury. Many social scientists would agree, the issues that some courts are trying to address, mainly cost and efficiency of jury trials, are not solved by adjusting jury size, but with positively influencing the public’s perception of jury duty.

For more detailed discussions of the impact of jury size on the justice system, please see these fascinating studies here and here.