Where were you on the night of the crime?

The wrongful conviction of a North Carolina man has helped inspire researchers on the other side of the planet to study just how well people can remember where they were and what they were doing at a particular time on a given day. Unsettlingly, their findings suggest that our own memories may prove to be surprisingly unreliable if they’re ever called upon to offer up an alibi for a crime.

In 1985, Ronald Cotton was wrongly convicted of a rape he didn’t commit, and he spent more than 10 years in prison before being exonerated by DNA evidence. A faulty eyewitness identification was mainly to blame, but Cotton also gave an alibi that couldn’t be corroborated—because, it turned out, he’d mistakenly recalled where he’d been the night of the crime.

The researchers, Yim Hyungwook of Hanyang University in South Korea and Simon Dennis of the University of Melbourne in Australia, cite Cotton’s case to introduce “The Fallacy of an Airtight Alibi,” published recently in the journal Psychological Science. They used a smartphone app to record data on 51 adults for a month prior to a memory test. (The data was collected before the pandemic, when people still went places.)

People’s memories of their own movements proved surprisingly faulty. Asked to identify where they were at a given time, participants were incorrect 36 percent of the time—even though the researchers had narrowed the possibilities down to just four choices.

The authors found strong evidence that participants confused days across weeks—when asked where they were three Tuesdays ago, they might incorrectly remember where they were two Tuesdays ago, for example. That’s exactly what happened to Cotton, and the authors conclude that such errors of alibi recall may be actually be quite common. People also tend to confuse hours across days, for example recalling something as happening at noon on the 2nd when it actually happened at noon on the 1st.

The authors believe their results can be used to alert investigators to the questions they should ask in order to catch the memory errors suspects are likely to make. Their findings will no doubt be of great interest to attorneys as well.

D.D.