The Legal Professional Opinion and Lay Citizens’ Judgment during Deliberation
MURAYAMA, Aya & MIURA, Asako
This study investigated whether professional opinion during deliberations influenced changes in jurors’ opinions, confidence of the opinion, and subjective performance of the deliberation. The saiban-in (lay judge) system was launched in 2009 in Japan to give ordinary citizens a direct role in the criminal judicial process. There, lay judges are selected separately for each trial and judge the case together with professional judges. Since the system gives professional judges a power for the verdict in both explicit and implicit manner during deliberations, there is a doubt whether lay judges can practically participate in and actively discuss based on their own perspectives.
In order to investigate the effect of such expert power during deliberations, a simplified mock jury was conducted in a lab setting. Three jurors (naïve participants) and one judge (a confederate who claimed guilty throughout the experiment) discussed guilt or innocence using a scenario that was based on an actual case. A total of 90 undergraduate and graduate students (30 groups) participated in the study. Opinion distributions (guilty as majority, tie votes, or innocent as majority) and forms of deliberation (either verdict-driven or evidence-driven) were manipulated.
The results showed that jurors tended to change their opinion in accordance with the judge. Moreover, jurors whose opinions coincided with the judge’s were more confident with their final decisions than jurors whose final decisions were different from the judge’s. The hierarchical linear model with a dependent variable of subjective performance had indicated that the agreement with the judge (both in group and individual level) and higher level of trust toward the judge both increased the level of subjective performance. Practical participation in deliberation had led higher subjective performance as well. Finally, the suggestions about the lay judge system and deliberation process were made based on the results of the study.
裁 判員裁判関連の発表でしたが、話をした人たち（おそらくアメリカ人）にとっては、専門家（裁判官）とトレーニングなしにいきなり評議をする、という状況が 信じられない、という感じでした。また、性別や年齢の構成はコントロールされているのか、という質問もされました（現状はまったくなにも決まりはないです ね）。
と言われました。確かに、研究しなければならないことはたくさんあるよう思 います。ただ、そこからまず何に着手するべきか、実際に裁判員制度にかかわっている現場の方にとってどのような研究が必要とされているのか、という点を しっかり考えなければならないと最近改めて感じています。できることから、進めていきます。