An alibi, in its most basic form, is a plea that one was not present when a crime was being committed. In practice, alibis can be considerably more complex than a simple narrative story. In the criminal justice system, alibis function as exculpatory evidence—a good alibi should rule out the alibi provider as a potential suspect in a case or provide reasonable doubt as to a defendant’s guilt in a criminal trial. Psychological research into the study of alibis is a relatively new area in psychology and law. This research paper summarizes some of the major findings and introduces the terminology of the existing psychological literature.
It is unclear how alibis are used in the early stages of criminal investigations, and the rules about how and when alibi evidence can be used in the court system vary greatly across jurisdictions. To function as exculpatory evidence, alibis must contain both a believable story and credible proof of the alibi provider’s whereabouts. Psychology is in a unique position to study alibis from both sides of the criminal process: Alibi generation relies largely on the memory of alibi providers and corroborating witnesses, and alibi evaluation occurs as the police, attorneys, and jurors decide the exculpatory worth of the alibi. The study of alibi generation can be informed by autobiographical memory research, and alibi evaluation can benefit from deception detection and suspect interrogation research. However, psychological research on alibis specifically is still relatively new and has focused thus far on the evaluation of alibis.
Alibis are evaluated according to their believability by detectives, prosecutors, defense attorneys, and jury members at different stages of the criminal process. For an alibi to be judged believable, credible proof of the alibi provider’s whereabouts is essential, and it can take one of two forms: physical evidence and person evidence. Credible physical evidence ties the alibi provider to a specific place and time; for example, an airline boarding pass includes time and location information and requires identification, making it highly unlikely that someone other than the ticket holder would be able to obtain the pass. The research to date has indicated that physical evidence corroborating an alibi carries considerable weight with alibi evaluators; mock jurors have rated alibis with supporting physical evidence as more believable than alibis without such evidence. However, evaluators do not seem to differentiate between physical evidence that might be easily fabricated, such as a cash receipt, and evidence that is more difficult to fabricate, such as a security video. Person evidence consists of testimony by an alibi corroborator, or alibi witness, as to the whereabouts of the alibi provider. Preliminary research has shown that mock jurors are quick to distinguish among alibi corroborators according to the corroborator’s relationship to the alibi provider. Specifically, corroborators who could conceivably have a motivation to lie for the alibi provider (such as a close relative or a good friend) are viewed as less credible than corroborators who have no relationship to the alibi provider. Some research has suggested that having someone close to a defendant as an alibi corroborator could be no better than having no alibi at all—mock jurors voted guilty just as often when the corroborating witness was a motivated other as when the defendant had no alibi defense at all.
Skepticism on the part of alibi evaluators may work well when evaluators are dealing with fabricated alibis offered by guilty defendants. However, difficulties may arise when evaluators are faced with alibis offered by innocent alibi providers. Innocent alibi providers could potentially fall a victim to normal memory errors, such as misremembering a date or time for a particular activity or failing to correctly recall their companions for a particular day. Unlike in a normal recollection situation, however, a normal memory mistake could look suspicious in the context of a criminal investigation. Preliminary investigations into the strength of alibis produced by innocent alibi providers suggest that people frequently misremember their actions for a previous date and have considerable difficulty producing any kind of proof for their whereabouts. Anecdotal evidence from past criminal cases suggests that evaluators may use a weak alibi as incriminating evidence, which could be especially worrisome for innocent alibi providers.
Continued research into the psychology of alibis will shed additional light on how police detectives, attorneys, and jury members deal with alibis in the context of more complex criminal cases. For example, it is unclear how evaluators would deal with multiple pieces of alibi evidence or how they would look upon innocent alibi providers who need to change their alibis in some way. Although the psychological research is limited at present, the literature is growing and will continue to uncover how alibis interact with other pieces of evidence in criminal trials.
References:
- Burke, T., Turtle, J., & Olson, E. A. (2007). Alibis in criminal investigations and trials. In M. Toglia, J. D. Read, M. Ross, & R. C. L. Lindsay (Eds.), The handbook of eyewitness psychology: Vol. 1. Memory for events (pp. 157-174). Hillsdale, NJ: Lawrence Erlbaum.
- Culhane, S. E., & Hosch, H. M. (2004). An alibi witness’ influence on mock jurors’ verdicts. Journal of Applied Social Psychology, 34, 1604-1616.
- Olson, E. A., & Wells, G. L. (2004). What makes a good alibi? A proposed taxonomy. Law and Human Behavior, 28, 157-176.
Return to the overview of Trial Consulting in Forensic Psychology.