National Police Procedural Justice Research Study Results Released


Cambridge Police Service was one of three agencies nationwide to take part in a recently published research study that examined the impact of procedural justice in policing. The large, randomized, multi-site field trial – the gold standard for evaluating effective policing strategies – was held in Cambridge, MA, Houston TX and Tucson AZ between 2017 and 2020 to test whether procedural justice training would an impact on police behavior, residents’ perceptions of the police and crime in high crime ‘hotspots’. Funded by Arnold Ventures and the National Policing Institute, researchers from the National Policing Institute, Northeastern University, Arizona State University School of Criminology and Criminal Justice, George Mason University, University of Pennsylvania and the Hebrew University of Jerusalem conducted the study.

Within each city, the researchers randomly assigned 40 high-crime hotspots — areas that show evidence of higher rates of violence and drug-related crime. For nine months, 4-6 volunteer officers (Group A) were assigned to proactive police patrols in 20 of the hotspots using traditional crime prevention strategies. During the same period, a separate set of volunteer officers (Group B) were assigned another 20 hotspots with an explicit focus on proactive patrols using only procedural policing in their interactions with residents. Prior to the study, Group B received 40 hours of intensive procedural justice training and was instructed to reduce crime AND build legitimacy with the community in assigned hotspots.

Procedural Justice and Cambridge Police Service

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

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

Cambridge Police have long been proponents 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 (beginning with a CPD-developed curriculum on police legitimacy and authority in 2010 and Fair and Impartial Policing in 2012) as well as its creation of the Office of Procedural Justice in 2018.

Study results
Police behavior was carefully monitored between the two groups over the 9-month study period. The monitoring included hundreds of hours of trips and observations of more than 500 police interactions with the public.

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

  • Officers trained in procedural justice (Group B) were found to be significantly more likely to listen to the public during an interaction, to demonstrate neutrality, and were more likely to treat people with dignity and respect. Importantly, given previous studies showing that disrespect has a particular impact on people who interact with the police, officers trained in procedural justice were significantly less likely to disrespect people. during these interactions.
    • In Cambridge, the effects of officers demonstrating greater respect and trustworthy motives in their interactions with the public were greater than in the other participating cities.
  • A survey of residents was conducted at each hotspot before and after the intervention in each of the three cities. Researchers found that residents associated with hotspots patrolled by officers trained in procedural justice were significantly less likely to see police on their street use unnecessary violence or harass residents. At a time when police violence and harassment have been at the forefront of criticism of policing, these findings are particularly important.
    • The majority of residents did not feel they had been harassed or abused in their neighborhood, nor did they believe that excessive force had been used by the participating Cambridge police officers.

  • There was a relative decline of approximately 14% in criminal incidents during the intervention in the hotspots of procedural justice conditions (cluster B) in the three-city study.
    • In Cambridge, there was a reduction in calls for service and a significant reduction in crime of 21% in hotspots patrolled by officers trained in procedural justice.
  • Across all three cities, there was a 60% drop in arrests by procedurally trained Group B officers compared to Group A officers.
    • There was no significant difference in the number of arrests in Cambridge due to the small number of arrests made in Cambridge – an indication of the already significant influence of procedural justice policies and procedures (9 total arrests between both groups; 4 for group B and 5 for group A).

“Procedural justice has long been an important guiding element in the culture of the Cambridge Police Service,” said Commissioner Christine Elow. “This study reflected its continued importance and how intensive training around procedural justice can lead to better outcomes – better interactions between officers and the community, and reduced crime – and that legitimacy can be built at the within hotspot policing, it also reaffirms that an investment in this essential training must be made in a consistent manner and that its impact must be well understood within the police service.

The study’s lead researcher, Professor David Weisburd, noted that “the Cambridge Police Service was a key participant in the study and showed considerable professionalism and commitment to the experiment. . This study shows that the police can simultaneously advance police reform and crime control. This study provides important direction for law enforcement across 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:


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