Prosecutorial perseveration: A reaction to public commitment

The startling number of cases in which prosecutors ignore clear-cut exculpatory evidence and persist in the prosecution of an almost certainly innocent suspect may be related to the public nature of these prosecutors’ commitments. Research has shown that people who make a public commitment to a decision are more likely to stick with their decision in the face of contrary evidence than people who did not make a public commitment. This study examined the effects of public commitment on undergraduate mock prosecutors’ decisions to prosecute in a fictional murder case. Half of the participants rendered an initial decision which was made public and half of the participants made no initial decision about the case. Participants were then given exculpatory evidence and asked to make a second decision. It was predicted that participants whose initial decision was made publicly would be more likely to remain consistent with this decision (i.e., continue to prosecute) than participants who did not make an initial decision. However, it was found that participants who made a public commitment were significantly less likely to decide to prosecute in the face of exculpatory evidence than participants who made no commitment. The implications of this unexpected finding are discussed.