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 one’s 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 don’t 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

• Our taxonomy/framework for classifying alibis is based on continuum of perceived credibility
• Alibi generation is essentially a time/space problem! Any and all evidence you gather to support your alibi must speak to BOTH the space you occupied and the time you occupied it.
• Physical Evidence: Evidence can be nonexistent (None), Easy to Fabricate, and Difficult to Fabricate
• Person Evidence: Credibility of people must come from both expertise and trustworthiness
• Motivated Other: Person concerned with outcome, high likelihood of motivation to lie, can rule out possibility of mistake (expertise high, trustworthiness low)
• Non-Motivated Stranger: Unconcerned with outcome, only saw once (trustworthiness high, expertise low). May be mistaken (like an eyewitness) but people not likely to consider this. Scientists may be a little leery about this category but most people would not likely distinguish too much between these and
• Non-Motivated Familiar Other: Unconcerned with outcome, could be acquaintance or someone who sees you on a regular basis (bus driver) but does not know you (trustworthiness high, expertise moderate/high).
• Neither of these w/likely motivation to lie, but Non-Motivated Familiar Other runs some risk of hidden motivation. Slightly more credible than Stranger, but both classes of Non-Motivated others are categorically different from motivated others! (psychological distance)

		Person Evidence
		None	M-O	NM-S	NM-FO
Physical Evidence	None	1	2	3	3
	Easily F	2	3	4	4
	Difficult F	5	5	5	5

 

Alibi Strength	Properties		Examples
	Person Evidence	Physical Evidence
No Alibi (1)	None	None	"I don’t 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