The effect of deliberation process and juror's prior legal knowledge on the sentence: the role of psychological expertise and crime scene photo

An experiment with simulated juries (N = 198) tested the impact of the deliberation process and two extra legal variables on the determination of sentence. Participants were either social science students without prior instruction in criminal law (prior legal knowledge: low-level group) or future professional magistrates completing their final year of training (high-level group). We manipulated the presence versus absence of (i) a non-diagnostic observation of the defendant by a psychology expert and (ii) a realistic crime scene photograph. After controlling for participants' gender and age, our results show that the high-level group was both less sensitive to the manipulated variables and more severe in their sentence than low-level jurors. We observed a post-deliberation increase in pre-deliberation bias such that the non-diagnostic psychological expertise had a stronger post-deliberation impact on the sentence. Finally, an unexpected effect showed that aggressive responses during the psychological observation tended to operate as exculpatory rather than accusatory evidence. Our results are discussed on the basis of previous research and proposals for future research are made.