The Cognitive Interview (CI) has been shown in over one hundred studies to enhance eyewitness recall. However, no study has explored whether the CI improves police job performance. The current study was the first to test the practical value of the CI in a criminal investigation, testing participants’ performance on key police tasks using either a perpetrator description elicited from a CI or from a standard police interview (SI).
In an earlier study, student witnesses were exposed to a simulated robbery and were then interviewed using either a CI or an SI to elicit a description of the robber (comprised of individual descriptors). In Experiment 1, a sample of student participants (N=320) completed two investigative tasks using the descriptors: (a) identifying the perpetrator from a group of ten potential suspect photographs; and (b) allocating hours among the top three potential suspects dictated by who should be the focus of the police’s time (i.e., investigative resources). Participants also subjectively assessed each descriptor’s value in terms of completing the tasks. Presentation methods to enhance the utility of the CI were also tested. Relative to the SI, the CI resulted in a near-30% increase in accurately identifying the perpetrator. Also, significantly more hours were allocated toward investigating the perpetrator using the CI as compared with the SI. Participants did not, however, subjectively value CI descriptors more than SI descriptors; and, the CI’s utility was not enhanced by the presentation methods tested.
Experiment 2 sought to reproduce and generalize the CI’s effect on investigative utility by using police officers (N=71) and student participants (N=67). As in Experiment 1, the CI significantly improved investigative performance in accurately identifying the perpetrator, and in allocating resources toward investigating the perpetrator. Police and students did not significantly differ in their performance of investigative tasks or in their utility ratings of the CI descriptors.
The current study was the first to find that the CI can be properly used by police in a criminal investigation. Investigating the actual perpetrator as opposed to an innocent suspect is likely to have a domino effect on subsequent phases of an investigation.
