A taxonomy of alibis is proposed involving two forms of supporting proof: physical evidence and person evidence. Levels of physical evidence and person evidence were combined to create 12 cells in the taxonomy. Participants (n = 252), who were asked to assume the role of detectives, evaluated alibis representing these 12 cells. The believability of the alibis generally followed the taxonomy's predicted pattern, but physical evidence, when present, tended to overwhelm the person evidence more than had been expected. In addition, alibi evaluators seemed to not consider the possibility that a stranger who corroborated an alibi might be mistaken about the identity of the person. Trait inferences regarding the alibi providers tended to follow the believability data, even when the traits themselves were not relevant to believability of the alibi. We call for the development of a literature on the psychology of alibis, recommend the taxonomy as a framework, and suggest several avenues of inquiry.

The criminal justice system relies heavily on eyewitness identification for investigating and prosecuting crimes. Psychology has built the only scientific literature on eyewitness identification and has warned the justice system of problems with eyewitness identification evidence. Recent DNA exoneration cases have corroborated the warnings of eyewitness identification researchers by showing that mistaken eyewitness identification was the largest single factor contributing to the conviction of these innocent people. We review major developments in the experimental literature concerning the way that various factors relate to the accuracy of eyewitness identification. These factors include characteristics of the witness, characteristics of the witnessed event, characteristics of testimony, lineup content, lineup instructions, and methods of testing. Problems with the literature are noted with respect to both the relative paucity of theory and the scarcity of base-rate information from actual cases.

The authors investigated eyewitnesses' retrospective certainty (see G. L. Wells & A. L. Bradfield, 1999). The authors hypothesized that extemal influence from the lineup administrator would damage the certainty-accuracy relation by inflating the retrospective certainty of inaccurate eyewitnesses more than that of accurate eyewitnesses (N = 245). Two variables were manipulated: eyewitness accuracy (through the presence or absence of the culprit in the lineup) and feedback (confirming vs. control). Confirming feedback inflated retrospective certainty more for inaccurate eyewitnesses than for accurate eyewitnesses, significantly reducing the certainty-accuracy relation (from r = .58 in the control condition to r = .37 in the confirming feedback condition). Double-blind testing is recommended for lineups to prevent these external influences on eyewitnesses.

An information-gain approach to the analysis and interpretation of eyewitness identification data is described. The information-gain analysis is grounded in Bayesian statistics, permitting the important role of prior probabilities to be explored. This approach also forces a more complete treatment of the data and reveals important patterns that have escaped previous attention in the eyewitness identification literature. Particularly important is the ability of information-gain analyses to make salient the exonerating value of eyewitness behaviors rather than just their incriminating value. Analyses of sample data sets show how the exonerating value of filler identifications and "not there" responses can actually exceed the incriminating value of identifications of the suspect at certain points in the distribution of prior probabilities.

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 0255) were asked to report four initial alibis Á each for a different time Á 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 quantityÁaccuracy trade-off framework.