Confessions make verdicts more legitimate because they are easy to communicate

In many judicial systems, confessions are a de facto or even de jure requirement for criminal conviction. Even if confessions are intrinsically convincing, this cannot explain why they should play such a paramount role. Instead, it has been suggested that confessions owe their importance to their legitimizing role. But why would confessions be particularly suited to justify verdicts?Justifications grounded in confessions might make better legitimizing tools because they can be more easily transmitted from one individual to the next, and thus spread in the population without losing their convincingness. 360 English-speaking participants were asked to evaluate the convincingness of one of three justifications for a verdict, grounded either in a confession, eyewitnesses, or circumstantial evidence, and to pass on that justification to another participant, who then had to perform the same task. In a second experiment, 240 English-speaking participants evaluated the convincingness of some of the justifications produced by the first group of participants. Compared to the other justifications, justifications based on confessions lost less of their convincingness in the transmission process (small to medium effect sizes). Modeling pointed to the most common forms the justifications would take as they are transmitted, and results showed that the most common variant of the justification based on a confession was more convincing than those of justifications based on eyewitnesses or circumstantial evidence (small to medium effect sizes). These results suggests that justifications for verdicts based on confessions are more easily transmitted, and thus can more easily legitimize verdicts.