The effects of group deliberation on capital jury verdicts: Bias attenuation or exacerbation?

Existing studies regarding the effects of capital punishment attitudes on jury decision making have consistently found that those holding pro-death penalty attitudes process information differently than those against the death penalty. These effects have been shown at all levels of processing including attention, weighting, and recall of attitude-consistent evidence presented at trial. Thus, the consistent finding in the literature that jurors who favor the death penalty are more conviction prone than those who oppose it is troubling given that it is those in favor capital punishment who are empanelled in capital trials. While this presents a problem for the impartial juror construct fundamental to the legal system, the studies used to reach such conclusions are individual level studies which examine only individual juror propensities. The role of capital punishment attitudes on decision making at the group level has largely been ignored, or left to inference. Given the possibility for group outcomes to be different than individual propensities, the question of whether juries would be similarly biased when it comes to capital punishment attitudes was empirically investigated in the present study. Davis’ social decision schemes (SDS) approach was used to examine processing in deliberating juries in order to determine if attitudinal biases favoring conviction evident at the individual level would be enhanced or diminished at the group level. Two types of juries were examined, homogeneous juries composed of those holding pro-capital punishment attitudes, and mixed juries, representing a range of attitudes towards the death penalty. In light of differences in information processing styles, bias enhancement in the form of increased conviction proneness was predicted for homogeneous juries and bias attenuation was expected for mixed juries. However, the results in the present study did not support these predictions. In fact, no evidence was found for bias of any type in the group process. Even the leniency bias, which is robust in other studies of jury decision making, did not emerge in the current study. Possible reasons for this are discussed including the fact that little evidence of bias was found at the individual level before deliberations. It is also conceivable that the type of case chosen and the moderate implications of guilt in the current study mitigated attitudinal biases.