Testis unus testis nullus

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Over the years, multiple people have been wrongfully convicted all over the world of which some had an alibi for the moment that the crime was committed to prove their innocence but were not believed. In the criminal justice system, there appears to be an assumption that innocent people can generate an accurate and believable alibi, which means that the alibi should be correct and be supported by strong evidence. For an innocent person, it can, however, be very difficult to provide such strong evidence as also appears in the cases of wrongfully convicted people where convincing evidence is often lacking. If people were not at the crime scene but elsewhere and they can remember where they were at that time and evidence to support their alibis, it is perhaps the best chance to prove their innocence. […]

The objective of the present study was to establish the base rate of alibis and its supportive evidence of non-offenders. Despite the fact that most non-offenders report an alibi, the vast majority of their alibis do not match the criteria of the perfect alibi by the police because strong evidence is lacking. The reported evidence is more often weak, and the evidence for their alibi differs depending on when the alleged crime was committed (i.e., during the morning, afternoon, evening, or night). In addition, an alibi without supportive evidence—the least believable alibi—is most likely to be expected during the night compared to other timeframes. An alibi supported with evidence is most likely to be expected on Saturday afternoon. The results show that the perfect alibi to which police detectives compare a suspect’s alibi is an illusion because only 7% of innocent people can present strong physical evidence (i.e., video recordings), and therefore, the base rate of alibis should be taken into account when evaluating alibis.

{ Journal of Investigative Psychology and Offender Profiling | Continue reading }