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We Need to Re-Think How Much Stock We Put in Alibis

Inconsistencies in alibis are an almost inevitable product of our flawed memory system, but they are still judged harshly by the legal system.

By Kate Wheeling


(Photo: Gabriel Bouys-Pool/Getty Images)

Quick: What were you doing three Thursdays ago at 9 a.m.? Were you sitting at work like usual? Or was that the day you got stuck in traffic and came in late? Most of us can’t recall a play-by-play of our typical days past. There’s usually no reason to do so. But what if, say, a police officer asks you to provide an alibi?

The legal system is already reckoning with research that calls into question the credibility of eyewitness testimony, recovered memories, lie detection methods, and traditional interrogation techniques and the confessions they produce. A new study suggests that our emerging understanding of memory in particular is primed to change both how we are asked to construct alibis and how those alibis are evaluated.

The problem, according to researchers from the John Jay College of Criminal Justice in New York and the University of California–Irvine, is that the process by which law enforcement extracts alibis, coupled with persistent misconceptions about how memory actually works, can put innocent people behind bars.

Here’s how things can go wrong: We tend to recall emotionally charged events in great detail, but people often don’t encode memories for mundane or routine events. So when an innocent person is asked about her whereabouts days, weeks, or months prior, she may have no memory of that time period. And the more time that’s passed, the more likely people are to forget details. Even the memories that we do encode are malleable; they are easily distorted by suggestion and apt to blend with other old memories overtime. Inconsistencies in our memories abound.

Police officers are often skeptical of alibis, and for law enforcement and laypeople alike, inconsistencies in alibis raise suspicion — even if the altered alibi is, in fact, a stronger one. Officers tend to equate an inadvertent inconsistency with a calculated lie, and that also holds true for prosecutors and jurors.“[W]hat starts as a normal memory error has cascading effects throughout the entire legal process,” the authors write.

Jurors will forgive lying under certain circumstances, according to Deryn Strange, an associate professor at John Jay College of Criminal Justice and co-author of the new study. “If you don’t say what you were doing because you were having an affair, for example, jurors will understand that and they will accept that as a reasonable explanation for essentially lying to police,” Strange says. “But they won’t accept that people can be wrong about where they were and what they were doing.” That’s because surveys consistently show that the majority of people still believe our memory works like a video camera, according to Strange.

“We tend to believe that, as soon as the police are involved in an investigation, as soon as your freedom is threatened, your memory will automatically be better, and it just doesn’t work that way,” Strange says.

Cases rarely hinge on only an inconsistent alibi, but the authors argue that it can set the tone for a person’s experience with the legal process, and even lead to a wrongful conviction when an inconsistent alibi is a defendant’s best evidence of innocence. The authors use a famous case of Ronald Cotton, which involved an inconsistent alibi and eyewitness misidentification, as an example:

When Ronald Cotton was arrested for the sexual assault of Jennifer Thompson, he quickly explained that he had been with his friends when the crime was committed. However, when no one corroborated his story, he realized his mistake: he had remembered the incorrect weekend. Thus, even though he was innocent — he was later exonerated after DNA testing — his alibi became ineffective, and probably appeared dishonest to the police.

Such cases might be avoided in the future if the legal system changes the way alibis are elicited or evaluated. Strange and her colleagues suggest, for example, that law enforcement ask suspects to account for a broader stretch of time, or construct a timeline of events surrounding the time of the crime, which might improve alibi accuracy. Of course, more research is needed on such techniques to find out what effect they might have on guilty suspects. “We can’t make things more difficult for the police,” Strange adds.

In the end, however, no one technique can fix our flawed memory. “The timeline technique might make people more accurate in their recall,” Strange says, “but if what they were doing was never encoded in the first place, then we’re never going to be able to help them generate an appropriate alibi.”