Policing Project visits California, part of national stop-data project

Policing Project Deputy Director Farhang Heydari recently traveled to California to learn more about how the state’s policing agencies are adapting to a new state law, AB 953, which required them to begin collecting stop data effective July 1, 2018. These site visits were an opportunity to learn how this first year of data collection is going and to hear what suggestions those agencies might have for other police departments embarking on data collection efforts.

This research is part of the Policing Project’s ongoing work on stop data and racial profiling with the goal to provide guidance for better data practices by police departments across the country, including that all jurisdictions collect individual-level stop data. As part of this work, we are partnering with the California Department of Justice and the Center for Policing Equity to develop a national guidebook on best practices for collecting and analyzing stop data. This project is expected to be completed in early 2020.

Why is stop-data so important?

Traffic stops are one of the most common ways the public interacts with the police, but these stops have often been linked to racially discriminatory practices, including racial profiling, as well as illegal searches and use of force incidents. Researchers from the Stanford Computational Policy Lab recently published a study analyzing data from nearly 100 million traffic stops conducted by dozens of policing agencies from 2011 to 2017. This study represents the most comprehensive public release and analysis of U.S. traffic stop records to date and has been widely covered by numerous media outlets.

Among other findings, CPL researchers found that black drivers were about 20 percent more likely to be stopped by police than were white drivers, and that black drivers were searched about 1.5 to 2 times as often. These findings mirror those found by previous studies, including one conducted by the Policing Project and the Stanford Computational Policy Lab in Nashville last year. These findings also mirror the lived experiences of communities of color, who know that they have borne the disparate brunt of police enforcement tactics.

At the same time, it is important to acknowledge that statistical disparities in traffic stops do not tell us much about an officer’s motivation for making a particular stop. Although important, rather than focusing on an officer’s individual intent, at the Policing Project we believe that detailed information about stop practices can provide great insight into a policing agency’s overall strategy and tactics. For example, the Policing Project used this type of data in Nashville to determine that proactive traffic stops were not an effective strategy in reducing crime, and to advise the department to redeploy officer resources toward more effective crime-fighting tools.

Stop data can thus provide valuable insights to both the public and a policing agency itself. But this can’t happen without the data.

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