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PNAS published an RCT of Procedural Justice training for police, to foster fair/respectful treatment of citizens. Quick take: High-quality RCT found no effect on community perception of police legitimacy (primary outcome) but suggestive effects on some other outcomes.

Program & Study Design:

  • The study randomly assigned 28 police officers in 3 cities (Tucson, Cambridge, Houston) to PJ training vs control, and randomly assigned 120 crime hot spots in the cities to be policed by trained vs control officers over a 9-month period. PJ training was an intensive, 5-day course.


  • The study found no significant effect on the study's primary pre-specified outcome - residents' perception of policy legitimacy (e.g., trust in police, obligation to obey police), as measured with community surveys.

  • The study found positive effects on some secondary outcomes (e.g., residents' perceptions of police misbehavior such as harrassment, observer measures of police behavior during ride-alongs) but not others (e.g., citizen calls for service - the main pre-specified measure of crime).

  • The positive effects are encouraging but I think best viewed as preliminary because (i) study measured many outcomes (which can cause false-positives), & (2) T officers might temporarily display expected PJ behaviors for observers during ride-alongs (social desirability bias).

  • Also, the 28 police officers in the sample had all volunteered for the study, so we don't yet know PJ training's effects on other police who don't volunteer.


  • Given the urgency of police reform, we need more high-quality RCTs like this to identify effective police training programs. Disclosure: My former employer, Arnold Ventures, funded this study.

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