Jury Verdicts: How Much Difference Does One Juror Make?

This study examined the following question: How well will a predictor of an individual juror's decision preference predict the verdict of the jury to which that individual belongs? A simulation study or "thought experiment " was performed. Using basic probability theory and the social decision scheme model of the jury decision-making process, it was possible to determine how strongly a juror characteristic would be related to his or her jury's verdict from a knowledge of how strongly that characteristic was related to his or her own personal verdict preference. For 12-person juries, the predictor accounted for less than 5% as much variance in juries' behavior as it did in jurors' behavior, regardless of the overall rate of conviction for jurors or the strength with which individual decisions were predicted. Although decreasing the jury size tended to increase this percentage, it remained quite small, even for dyads. Quite similar results were found when alternative decision schemes were employed. It was also shown that when the members of the jury are uniformly high or low on some characteristic, the predictor variable is generally related to group verdicts more strongly than it is to individual verdicts.