The Effect of Evidence Timing and Witness Motivation upon Juror Evaluations of Alibi Witnesses and Defendants

Abstract

The present study examined whether evidence timing and witness motivation affect mock jurors’ decisions. Participants read a mock case where the defendant's alibi was not corroborated, corroborated by a motivated alibi witness (with prior relationship with the defendant), or corroborated by an unmotivated alibi witness (with no relationship with the defendant). Where present, the alibi corroboration was provided either at a timely point in the police investigation, or delayed to ‘ambush’ the court. Supporting prior literature, timely alibis were seen as significantly more reliable when substantiated by an unmotivated alibi witness than by a motivated witness. Additionally, when the alibi witness was unmotivated, timely evidence was perceived as significantly more reliable than ambush evidence. However, alibi corroborator and timing did not have a significant effect on either case verdicts or perceptions of defendant reliability. The findings suggest that defendants may not be unfairly advantaged if their ambush alibi is admitted into court.