Suspicion and Police Decision Making

Police officers make decisions each day to stop and search civilians, with important consequences for public safety, civil liberties, and relationships between law enforcement agencies and the communities they serve. Identifying the effects of police stop, question, and frisk (SQF) practices is challenging due to data limitations, and the empirical evidence to date has been mixed. Analyses of aggregate outcome data cannot account for decisions to not stop civilians, are subject to reporting biases by officers, and have limited capacity for assessment of individual-level variation in stop decisions. Public policy scholar Amanda Charbonneau, legal scholar Hannah Laqueur, and psychologist Jack Glaser propose to examine police decision making and ways to improve the accuracy and equity of police SQF decisions. The project is a collaborative effort involving the PIs and the Stockton and San Francisco police departments that will allow the PIs to collect and analyze quantitative data from simulations, surveys and officers in the field.

The PIs propose to conduct a randomized controlled trial (RCT) to test the hypothesis that instructing officers to focus on specific behavioral indicators of illegal activity can improve the accuracy and equity of simulated policing decisions. They will also assess the relationship between officer-reported reasons for stops and outcomes in the field, namely arrests and discovery of contraband. The PIs will also examine the psychology of suspicion in the context of police decision-making and its relationship to the number, effectiveness, and equity of officers’ simulated and real-world SQF decisions. Even though suspicion is key to stop and search decisions, and reasonable suspicion is the governing legal standard, little is known about the effects of trait- and state-level suspicion on policing decisions, nor the potential interactions between the guidance provided to officers and individual differences that might shape SQF decisions. The PIs also plan to evaluate the extent to which officer-recorded reasons for SQF decisions and individual differences between officers are predictive of outcomes reflected by the performance data. The findings could inform policies and trainings to advance the broader objectives of increasing the effectiveness and equity of policing decisions.