Police officers' credibility judgments: Accuracy and estimated ability

A study was conducted to examine Spanish police officers' and nonofficers' lie- and truth-detection accuracy, as well as their estimated detection ability. The participants were 121 police officers and 146 undergraduates who watched videotaped truthful and deceptive statements. They had to indicate: (1) whether each statement was truthful or deceptive, and (2) how good police officers were, in comparison with the general population, at detecting the truthfulness or deceptiveness of a statement. Results indicate that police officers' accuracy was not higher than that of nonofficers, rather, while the officers reached an accuracy rate close to chance probability, the undergraduates surpassed that probability. Officers had a very strong tendency to judge the statements as deceptive; this made them less accurate than the students in judging the truthful accounts, while both groups reached a similar accuracy when judging the deceptive ones. Both occupational samples considered that the police are more capable of identifying truths and lies than the general population. However, this belief was stronger among the officers themselves than among the nonofficers. No significant correlation between estimated ability and accuracy was found for either sample. The results are explained in terms of the participants' wrong beliefs about the cues to deceit and the socialization process that police officers undergo, which would increase their confidence and perceived ability while hindering their learning of the actual indicators of deceit. The need for officers to receive training is emphasized, and some directions are given on how this training should be carried out.