‘But can you prove it?’ – examining the quality of innocent suspects' alibis

Despite an assumption in the legal system that innocent people can generate accurate alibis, little research has examined the process of alibi generation. The current study examined this process with respect to three theoretical reasons why innocent suspects may fail to generate convincing alibis: they may lack the necessary memory, generate mistaken alibis, and generate weak or uncorroborable alibis. Undergraduates (N=255) were asked to report four initial alibis – each for a different time – along with corroborating physical and person evidence. Participants attempted to corroborate that evidence before returning 48 hours later. Upon return, participants reported their investigated alibis for the same four time periods. Results indicated that, despite participants' willingness to generate initial alibis, a substantial proportion of these alibis (36%) were mistaken, requiring either a change in narrative or a change in corroborating evidence. The majority of investigated alibis relied on evidence that evaluators would consider weak. Distant-past alibis were more likely to be mistaken than near-past alibis. Results indicate that innocent alibi providers may find convincing alibis difficult to generate, and we explain these results within a quantity–accuracy trade-off framework.