In 1984, Jennifer Thompson was raped in her student flat by a stranger. Five days later, Ronald Cotton was questioned about his alibi. He explained that he was together with friends at the time of the crime. But shortly after, he changed his statement: He had slept on the couch in his mother’s house mother at the implied time. Is this statement to be trusted? Did Cotton lie initially?
The latter is what 80 percent of investigators assume, according to research conducted in the US: If suspects change their alibi later on, the most probable cause is that they lied before. To test this assumption, two American researchers asked 255 students to provide an alibi statement for four time periods in the past. Most participants, namely 88 percent, remembered the specified periods and provided a statement about their whereabouts. In the second part of the study it became trickier: participants had to provide evidence in support of their statement. In a second testing session, about one third of the participants indicated that they had been mistaken during the first session and that they had to correct their alibi. A follow-up study showed that most alibi statements contained inconsistencies. These inconsistencies were found for all aspects of the statement: the persons involved, locations, time and chronology of events. The authors conclude that inconsistencies in alibis are a natural side product of our imperfect memory that occur in suspects, much as they do in eyewitnesses.
But how did it end for Ronald Cotton? After his first statement, he realized that he had confused two weekends and therefore had to correct his alibi. In 1985, he was convicted to life in prison (partly) because his alibi was not believed. Today, we know that he was innocent, thanks to DNA evidence. He was released from prison in 1995.
Dysart, J. E., & Strange, D. (2012). Beliefs about alibis and alibi investigations: A survey of
law enforcement. Psychology, Crime & Law, 18, 11-25.
Olson, E. A., & Charman, S. D. (2012). ‘But can you prove it?’ – examining the quality of
innocent suspects’ alibis. Psychology, Crime & Law, 18, 453-471.
Strange, D., Dysart, J., & Loftus, E. F. (2014). Why errors in alibis are not necessarily
evidence of guilt. Zeitschrift für Psychologie, 222, 82-89.
Written by Melanie Sauerland, this blog was originally published in German at de.in-mind.org