Trial or Error? Police Updating in Investigative Stops

• In Event: Stop and Frisk: Some Outstanding Questions

Abstract

Theories of rational behavior assume that people make decisions where the benefits of their acts exceed their costs or losses. If those expected costs and benefits change over time, behavior will change accordingly. In this context, police stops that achieve any of several goals – constitutional stops, stops that lead to ‘good’ arrests or summons, or that lead to seizures of weapons, drugs or other contraband (stolen property) – should signal to officers the features of a stop that increase its rewards or benefits. Conversely, officers should also learn the features of unproductive stops. A rational actor would pursue “good stops” and avoid “unproductive stops” by updating their knowledge of these features through experience. This paper analyzes data on 5.5 million Terry stops from 2004-15 to estimate the extent of updating by officers. By comparing productive and unproductive stops, the analysis estimates the weights or values - an experience affect - that officers assign to the signals of each type of stop outcome. These estimates are disaggregated to persons from different racial or ethnic groups, to specific crime types, to the neighborhood contexts of the stops, and to specific management and supervision contexts. The analysis also considers whether updating is sensitive to different signals of suspicion, distinguishing between behavioral cues and subjective factors. These results will inform theory, policy and legal dimensions of police practice.

Author

• Jeffrey Fagan, Columbia University