The Tine Blue Line: Traffic Stops in the Wake of Police Fatalities

• In Event: Evaluating Policing Strategies: Administrative Systems, Training, and Enforcement Outcomes

Abstract

Police officers possess considerable discretion in the exercise of their authority (See, e.g.  Anderson v. Creighton, 483 U.S. 635 (1987)). However, recent scholarship has begun to illustrate the ways in which cognition and judgment can be affected by irrelevant, external, forces—often through an emotional channel (see Doleac, 2022).

Given these two phenomena, we ask how police exercise of discretion might be affected by an emotional shock. To answer this question, we examine how traffic enforcement changes following the death of a nearby law enforcement officer.

Annually, over a hundred law enforcement officers fall in the line of duty, a substantial fraction of whom are victims of felonious acts. Public memorials such as the Officer Down Memorial Page website and the dedication of public spaces to fallen officers attest to the broader impact of officer deaths. The death of a fellow law enforcement officer may constitute an emotional shock sufficient to alter police exercise of discretion. Leveraging a quasi-experimental design, our research uses event-study and generalized difference-in-differences analyses to investigate individual police stops in the aftermath of a felonious officer death. We draw on the extensive Stanford Open Policing Project dataset, which records over 200 million individual traffic stops across multiple state and local police departments. The database contains detailed information for each stop, including officer demographics, stop outcomes, and driver characteristics.

We use two different data sources to identify officer deaths. First, the FBI’s Law Enforcement Officers Killed in Action (LEOKA) data serves as our primary source. Second, we supplement LEOKA with the Officer Down Memorial Page (ODMP) for officer demographic information, date, location, circumstance, and cause of death. ODMP data has been collected through a combination of automated data scraping, and manual verification.

Our results indicate that the death of a police officer impacts the traffic enforcement patterns in the following days. First, we find that police officer killings lead to an uptick in the volume of traffic stops, particularly in the immediate aftermath. Second, we explore changes in the demographic composition of drivers stopped in the days and weeks following the incident. We find a disproportionate increase in stops among Black drivers compared to White drivers. Moreover, we show that, conditional on a Black driver being stopped, there is an increase in warnings rather than citations, suggesting that these stops may be pretextual in the aftermath of a felonious officer killing.

Author

• Kathryn Johnson, Northwestern University
  Presenting Author