Results From National Police Research Study on Procedural Justice Published

The Cambridge Police Department was one of three agencies in the country to participate in a recently published research study that examined the impact of procedural justice in policing. The large multi-site randomized field trial--the gold standard to evaluate effective policing strategies--was held in Cambridge, MA, Houston TX, and Tucson AZ between 2017-2020 to test whether procedural justice training would impact police officer behavior, residents’ perceptions of police, and crime in high crime “hot-spots.” Funded by Arnold Ventures and the National Policing Institute, researchers from the National Policing Institute, Northeastern University, the Arizona State University School of Criminology and Criminal Justice, George Mason University, University of Pennsylvania, and The Hebrew University of Jerusalem conducted the study.

In each city, researchers randomly assigned 40 high crime hot spots – areas that have evidence of higher rates of violence and drug crime. For nine months, 4-6 volunteer officers (group A) were assigned to proactive police patrols in 20 of the hot spots using traditional crime prevention strategies. During the same timeframe, a separate set of volunteer officers (group B) were assigned 20 other hot spots with an explicit focus on proactive patrols using procedurally just policing in their interactions with residents. Prior to the study, group B received 40 hours of intensive procedural justice training, and were told to reduce crime AND build legitimacy with the community in the assigned hot spots.

Procedural Justice & the Cambridge Police Department

Procedural justice deals with the process, not the outcomes of policing. Instead of prescribing outcomes, procedural justice establishes four basic rules when interacting with community members:

  1. Listen and allow a person to explain their side of the story.
  2. Be transparent about decisions that are made.
  3. Demonstrate care and concern for a person’s safety.
  4. Treat people with dignity and respect.

The Cambridge Police has long been a proponent of procedural justice and ensuring legitimacy within the department. This commitment was exemplified when it was one of the first departments in the country to implement procedural justice in training (starting with a CPD developed curriculum on legitimacy and police authority in 2010 and Fair and Impartial Policing in 2012) as well as its creation of the Office of Procedural Justice in 2018.

Results of Study
Police officer behavior was carefully monitored between both groups during the 9-month study period. The monitoring included hundreds of hours of ride-alongs and observations of over 500 police interactions with the public.

The study demonstrated that intensive police training in procedural justice can improve police behavior in crime hot spots where proactive policing interventions are implemented, and has the potential to reduce arrests, decrease crime, and enhance the public opinion of police.

  • The procedural justice-trained officers (group B) were found to be significantly more likely to listen to the public during an interaction, show neutrality, and were more likely to treat people with dignity and respect. Importantly, given prior studies showing that disrespect is particularly impactful on people who have interactions with the police, the procedural justice-trained officers were significantly less likely to show disrespect to people in these interactions. 

    • In Cambridge, there were stronger effects of officers exhibiting greater respect and trustworthy motives in their interactions with the public than the other participating cities.

  • A survey of residents was conducted at each hot spot before and after the intervention in each of the three cities. Researchers found that residents associated with the hot spots patrolled by the procedural justice-trained officers were significantly less likely to see police on their street as using unnecessary violence, or harassing residents. In a period in which police violence and harassment have been at the forefront of critiques of policing these findings are particularly important.

    • Residents overwhelmingly did not feel like they were harassed or mistreated on their block, nor did they believe excessive force was used by participating Cambridge police officers.


  • There was about a 14 percent relative decline in crime incidents during the intervention in the procedural justice condition (group B) hot spots across the three-city study.

    • Within Cambridge, there was a reduction in calls for service and a significant crime reduction of 21% in the hot spots patrolled by the procedural justice-trained officers.

  • Across the three cities, there was a 60 percent decline in arrests by the procedural justice-trained officers in group B compared to the officers in group A.

    • There was no significant difference in the number of arrests in Cambridge because of the small number of arrests made in Cambridge—an indication of the already substantial influence of procedural justice policies and procedures (9 total arrests between the two groups; 4 for group B and 5 for group A).

“Procedural justice has long been an important guiding tenant within the culture of the Cambridge Police Department,” said Commissioner Christine Elow. “This study reflected its continued importance and how intensive training around procedural justice can lead to enhanced results -- better interactions between officers and the community, and a reduction in crime – and that legitimacy can be built within hot spots policing. It also reaffirms that an investment in this critical training needs to be made on a consistent basis and its impact well understood within police departments.”   

The Principal Investigator of the study, Professor David Weisburd, noted that the “Cambridge Police Department was a key participant in the study, and showed tremendous professionalism and commitment to the experiment. This study shows that the police can both advance police reform and crime control simultaneously.  This study provides important guidance for police throughout the United States.”

More information about the study is available in the Proceedings of the National Academy of Sciences of the United States of America:

Page was posted on 5/6/2022 11:19 AM
Page was last modified on 5/25/2022 11:25 PM
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