The case of Ronald Cotton
A good example of the consequences of an inconsistent alibi is the case of Ronald Cotton, a 22 year old man, who is convicted in 1985 for the rape of Jennifer Thompson on the 28th of July 1984. That summer holiday, Ronald spends his time partying and loses track of time. Beginning of August the police ask him for his alibi on that particular night. He tries to recollect his whereabouts and tells the police that he went to his brother’s home and afterwards had some drinks with friends. Shortly after that, he speaks with his mother who tells him he has been wrong: that night he spent the night at her home on the couch. Ronald panics at the thought that he has provided a wrongful alibi to the police. This mistake and the recognition by Jennifer of Ronald in a badly executed line-up lead to the unjust conviction of Ronald to a lifetime imprisonment. In 1995, it becomes clear that Ronald could not have been the rapist because his DNA does not match the DNA found at the crime scene. He is released after 10 years of unjust imprisonment.

When is an alibi credible?
A correct alibi evaluation has the potential of accurately differentiating between innocent people and potential suspects at the beginning of a police investigation. Unfortunately, these evaluations are not always flawless. That became clear from wrongful conviction cases. Both mock jurors and police detectives only consider a consistent alibi that is supported by strong evidence to be believable. Yet, it is not uncommon to report an alibi that needs alterations because of, for example, memory errors or to cover up a secret relationship. Strangely enough, the alteration of an alibi because of salacious activity appears to strengthen its credibility.

Science and practice
Nieuwkamp shows in his dissertation that both generating a believable alibi and subsequently determining its believability in practice are difficult tasks. Relying purely on the strength of the evidence does not seem to be sufficient to assess an alibi. Nieuwkamp is one of the first researchers that have involved police detectives in research into the credibility of alibis. Nieuwkamp concludes in his PhD research that detectives should take into account the content of the alibi, the feasibility of (strong) supportive evidence and the fallibility of the suspect’s memory. He states that science and practice can reinforce each other in the assessment of alibis. Future research, consisting of collaboration between scholars and various groups of practitioners, remains needed to further enhance the assessment of an alibi in practice in order to prevent wrongful convictions and releases. Ricardo Nieuwkamp’s research is funded by NWO.