Not separate but equal? The impact of multiple-defendant trials on juror decision-making

ABSTRACT

Suspects accused of involvement in the same crime can be tried in one multiple-defendant trial. While research has long demonstrated the difficulties of being a juror, no published work has examined whether multiple-defendant trials compound these difficulties. The current research recruited both student and community samples to determine whether trying multiple defendants would increase conviction rates for individual defendants. Every participant watched one of three trial videos – a single defendant against whom the State had a strong case (single-strong), a single-defendant against whom the State had a weak case (single-weak), or a multiple-defendant trial combining both defendants (multiple-defendant). The findings demonstrated an overshare effect – when the defendants were tried together, overall conviction rates for both defendants increased relative to when they were tried alone, though the pattern of results differed by study sample. Although we are unable to provide a definitive mechanism underlying the results, the best explanation seems to be that multiple-defendant trials prompt jurors to engage in a joint evaluation of the defendants, rather than single evaluations of each. Consequently, participant-jurors’ perceptions of each defendant are impacted by how they compare with one another. Thus, the current research casts some doubt on the fairness of multiple-defendant trials.

KEYWORDS:

• Jury decision-making
• adjudication
• juries
• multiple defendants
• sentencing

Acknowledgments

The coauthors would like to thank Bridget C. Baron for her important contributions during data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. Upon closer inspection, it does appear that there were a few more high scores among the community participants than the student participants; thus, it is possible that a few went back to inflate their scores (and ensure they were awarded additional compensation). To further examine this possibility, we conducted a correlation analysis to determine whether duration was related to accuracy (because going back to re-watch elements of the video would require additional time), and found no evidence of a relationship, r(42) = 0.21 [−0.10, 0.48], p = 0.193 (weak); r(44) = 0.07 [−0.23, 0.36], p = 0.632 (strong). Further, the average duration for the community participants was 87.8 minutes in the multiple-defendant condition, 69.8 minutes in the single strong, and 55.7 in the single-weak. Considering the varying length of the trial videos, on average, community participants required 20–25 minutes to read through all the study instructions (e.g. informed consent) and complete all of the questionnaires. Given the length of the questionnaires, it is reasonable to assume that participants were not doing much beyond what they were instructed to do in those 20–25 minutes.

Additional information

Funding

This material is based upon work supported by a Psi Chi Graduate Research Grant as well as a National Science Foundation Graduate Research Fellowship to the first author under Grant No. 202-18-94-00. A subset of the data in this paper was presented in a talk at the annual American Psychological Association conference in Honolulu, HI.