Effects of prior interpretation on situation assessment in crime analysis

A main threat to objective information processing in crime investigation teams is the tendency to focus on one particular interpretation only. To prevent such tunnel vision or ‘groupthink’, an investigation team can call in a crime analyst, and ask him or her to give a fresh and independent account of the evidence at hand. However, before they examine the case, crime analysts are often already aware of the scenario currently favoured by the team. In our experiment, we investigated whether such prior knowledge can jeopardise the independence of the analyst's advice. Thirty‐eight professional crime analysts were asked to generate causal scenarios for two different cases and to indicate how the team should continue their investigation. Before beginning their analysis, half of the crime analysts received a realistic prior interpretation, such as might have been constructed by an investigation team. The results show that when given a prior interpretation, both experienced and inexperienced analysts considered the scenario suggested therein as more likely, and made recommendations for further investigation accordingly. We explain these findings by suggesting that analysts temporarily adopted the perspective of the investigation team, and that such temporary commitment by itself increased confidence in the hypothesis at hand (Koehler, 1991). This research supports previous research on the impact of prior theory on judgement, and extends it to an important real world domain where mistakes can have serious consequences. We recommend that in cases where the crime analyst is asked to give an objective assessment, he or she should not be informed about the interpretation of the investigation team until after the analysis has been conducted. Copyright © 2007 John Wiley & Sons, Ltd.