Investigating investigators : how presentation order influences investigators’ interpretations of alibi and bystander witness evidence




Dahl, Leora Catherine

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Eyewitness identification evidence is often essential in criminal investigations, yet little is known about how police investigators evaluate identification evidence. This research simulated a police investigation by having participant-investigators obtain information about a crime, examine a database of potential suspects with the goal of choosing a likely suspect for the crime, and evaluate an eyewitness's lineup identification decision. Experiments 1 and 2 examined the effect of order of presentation of the eyewitness decision. When the eyewitness identified the investigator's suspect, ratings of the suspect's guilt were similar regardless of when the eyewitness decision occurred. However, when the witness reported that the culprit was not present in the lineup, a recency effect occurred (the information that was presented last had a larger impact). Experiment 3 continued to examine order effects while also examining how investigators evaluated alibi information and eyewitness testimony when they had already identified a suspect in the case. The investigators evaluated alibi evidence that was either strong or weak (in regards to exonerating the suspect) and eyewitness evidence involving a witness who either identified the investigator's suspect or rejected the suspect (by not making an identification). The order of presentation of the alibi information and eyewitness testimony was manipulated such that half of the participants received the alibi information before the eyewitness testimony while the other half received the alibi information after the eyewitness testimony. Both the eyewitness decision and alibi evidence affected ratings of guilt. A recency effect was present only in the ID Suspect/Strong alibi conditions, such that when investigators saw the witness identify the suspect and then received the strong alibi, they rated the likelihood that their suspect had committed the crime as lower than when they received the strong alibi first and then saw the witness identification. Otherwise, the two forms of evidence had an additive effect. Together, these studies provide a valuable examination of the influence of presentation order and the importance of different forms of evidence on role-playing police investigators.



Eyewitness identification, Criminal investigation, evidence