The Psychology of Alibis or

Why We Are Interested in the Concept of Alibi Evidence

Gary L. Wells & Elizabeth A. Olson

Iowa State University

January 2001

We are interested in the psychology of alibis. Yet, there is little if any empirical literature on alibis.

You are reading some of our earliest musings on developing a literature on the psychology of alibis. (See this link to a recent case in which a video alibi proved innocent a person who was identified by eyewitnesses and who confessed!)

Definition of alibi: a plea that one was elsewhere from the scene of a crime (Webster's) OR A defense that places the defendant at the relevant time of the crime in a different place than the scene involved and so removed therefrom as to render it impossible for one to be the guilty party (Black's Law Dictionary)

"no alibi" has 2 components: No memory = no alibi by definition

I was alone = no alibi by common usage

It is important to note that alibis can be either true or untrue. True alibis are accurate accounts of oneís whereabouts. Untrue alibis, however, can be untrue for a variety of reasons. The person providing the alibi could be the culprit and would be providing a fabricated alibi. Or someone may provide a fabricated alibi to conceal the embarrassing nature of their activities (i.e. a man was with his mistress at the time). Another type of untrue alibi is the mistaken alibi: the person providing the alibi believes it is true at the time they give it; only later is it discovered that the person was actually somewhere else. He or she has committed an honest memory error, but we believe that these mistaken alibis are not seen as honest mistakes but as indicators of guilt. (See the Ronald Cotton case in which an untrue alibi factored into the imprisonment of an innocent man.)

So we know what an alibi is, but we donít know what makes an alibi good. In our opinion a strong, believable alibi is one that keeps the person providing the alibi OUT of hot water: either by keeping him or her out of prison or out of the suspect pool altogether.

Alibi Credibility

Of course, the mere assertion by a defendant that one was at some place other than the crime at the time of the crime is not sufficient to establish an alibi. One must have some type of proof in order for a given alibi to be considered credible. In effect, the person asserting an alibi defense must create some type of evidence that solves a time/space problem: the evidence MUST speak to both the space one was in and the time that one occupied that space.

A Taxonomy of Alibis

We have been developing a taxonomy of alibis to help codify what is a strong, believable alibi. Our taxonomy follows the approximate order with which we think alibis will be evaluated in terms of their credibility in the eyes of most people (including police, judges, lawyers, and jurors). Our taxonomy of alibis factorially combines multiple levels of two types of variables, namely physical evidence (such as receipts or video) and person evidence (someone who can vouch for your whereabouts). We are continually refining the taxonomy, so if you want to use it, you might check with us about what the latest version might be or what we have learned from using the taxonomy.

The purpose of our alibi taxonomy is to facilitate research. We want to know more about how people evaluate alibis. We have developed some hypotheses about alibis based on our general understanding of how people make complex judgments. For instance, we know that observers tend to underestimate the influence of situational factors on the behaviors of another person. This "fundamental attribution error" can lead people to not appreciate the difficulties associated with being placed in a particular role (Ross, Amabile, & Steinmetz, 1977). Frequently, a person is thrown into the role of "alibi provider" when it is suspected that the person committed a criminal offense. We hypothesize that people underestimate the difficulty that innocent suspects have providing proof of their alibi, especially under certain conditions. As a result, weak alibis could actually be perceived as incriminating evidence under conditions where they ought to be considered neutral.

The Alibi Process

We have begun to develop a model of the alibi process which highlights some exciting possibilities for the psychology of alibis. There are, in our opinion, two general psychological domains within which the alibi process operates: the generation domain and the believability domain.

The generation domain includes within it issues of memory¾ the autobiographical memory of the alibi provider as well as the memories of the people who are asked to corroborate an alibi. This domain has two phases:

1.) Story Phase: This is the provision of the memory statement by the alibi provider.

2.) Validation Phase: In this phase, the evidence offered in support of the alibi is researched. This can be undertaken by many people, including the alibi provider and police investigators.

The process now moves into the believability domain, which concerns how people evaluate alibis.

3.) Evaluation Phase: This phase is undertaken by anyone who experiences the alibi¾ police, newspaper consumers, lawyers. People decide for themselves the strength of the alibi.

4.) Ultimate Evaluation Phase: An alibi may not always reach this phase. This is the definitive determination of the truth of the alibi when it is presented in court, and it is undertaken by judges or juries. Other evidence surrounding the case will influence this phase.

Before examining the taxonomy (below), you should review our taxonomy notes.

Taxonomy Notes

There is some arbitrariness in our model. The people variable has more levels, and is thus more impactful. The psychological difference between no people and one person is not necessarily the same as the difference between no evidence and easily fabricated evidence. We have some lines drawn between categories but specific ordering between categories will be sensitive to specific operationalizations of properties.

Factorial Taxonomy

Person Evidence
Physical Evidence
Easily F
Difficult F


Full-Page Taxonomy

Alibi Strength
Person Evidence
Physical Evidence
No Alibi (1) None None "I donít even remember"

"I was home alone in bed"

Weak (2) None Easily Fabricated Computer file showing creation time

Store receipt for cash purchase

Motivated Other None "I was home with Mom"

"My best friend and I were playing video games"

Moderately Weak (3) Motivated Other Easily Fabricated "I was shopping with my sister"
Stranger None Subway security officer

Elderly couple at the next campsite

Familiar Other 

Not Motivated

None Bus driver on your usual route
Moderately Strong (4) Stranger Easily Fabricated Person in tour group corroborates and you have a dated/timed ticket stub
Familiar Other

Not Motivated

Easily Fabricated Signed, dated receipts from shopping and your usual bus driver remembers 
Strong (5)
None Difficult to Fabricate Plane ticket stub

Security camera video at another location

Motivated Other Difficult to Fabricate "I was flying to Vegas with my wife"
Stranger Difficult to Fabricate Plane ticket and the flight attendant
Familiar Other 

Not Motivated

Difficult to Fabricate On camera with retinal scan while checking through security at a defense contractor company