On this page, the Crime and Justice Policy Lab has curated research relevant to our areas of work.

Analyzing the Impact of Baltimore’s Group Violence Reduction Strategy in the Western District

GVRS Public Infographic

Crime and Justice Policy Lab, University of Pennsylvania (Jan 2024)

This analysis suggests The team’s preliminary estimates are that, in the 18 months after its introduction in January 2022, GVRS was responsible for reducing homicides and shootings in the Western District by roughly a quarter, and carjackings by about a third, with no evidence that these crimes moved to other parts of the city. Importantly, despite the important role played by police in this intervention, the preliminary analysis does not detect an increase in overall arrests or those for minor offenses due to GVRS.”

An Evaluation of the Group Violence Intervention (GVI) in Philadelphia

Ruth Moyer (Feb 2023)

This evaluation suggests “the current GVI implementation in Philadelphia has been associated with significant reductions in group member involved firearm violence. The continued effectiveness of the implementation will likely depend on a range of factors, including necessary adjustments to evolving group activity and firearm violence.”

Crime Prevention Through Intelligence and Information Sharing: An Evaluation of an Information Intervention at the Philadelphia Police Department

Aaron Chalfin, Greg Ridgeway, John MacDonald, Rachel Ryley (July 2022)

“The evidence on the effectiveness of the phones is mixed. On the one hand, it is clear that a year after the phones were deployed, relatively few officers are using their phones regularly. While some officers have taken advantage of the phones to interact with members of the community, perform business checks, make 311 reports to address physical disorder, and pass intelligence reports on to analysts at the city’s Crime Information Centers (CICs), these activities are driven by a small number of enthusiastic adopters rather than broad interest among a large group of patrol officers.”

Fulfilling the Promise of Public Safety: Some Lessons from Recent Research

Ben Struhl, Alexander Gard-Murray (May 2022)

“Many American communities are wrestling with how to reform their approach to public safety in the wake of police killings, particularly of Black men. There are many ideas for what the right reforms might be, ranging from minor policy tweaks to wholesale replacement of departments. To help communities as they sort through these ideas, we review real experiences with policing reform, highlighting wherever possible the best scientific evidence on the subject.”

Estimating the effects of shrinking the criminal justice system on criminal recidivism

Charles E. Loeffler, Anthony A. Braga (May 2022)

“We examined the impact of Raise the Age (RTA) in Massachusetts, which increased the maximum jurisdictional age for its juvenile court in late 2013. Using statewide re-arraignment data and a difference-in-differences research design comparing affected 17-year-olds to unaffected 18-year-olds, we find that RTA increased recidivism for affected 17-year-olds. The observed increases in recidivism were especially large for 17-year-olds without prior justice involvement. This result may stem from the more extensive use of pretrial supervision or the diminished deterrence of prosecution within the Massachusetts juvenile justice system.”

Association Between Structural Housing Repairs for Low-Income Homeowners and Neighborhood Crime

Eugenia C. South, John MacDonald, and Vincent Reina (July 2021)

“The results suggest that structural, scalable, and sustainable place-based interventions should be considered by policy makers who seek to address crime through non–police interventions.”

Click here to learn more about the Basic Systems Repair Program. 

Low-Touch, Misdemeanor Diversion Programs with Record Expungement Reduce Reconviction RatesWhite Paper | Full Paper

Viet Nguyen (April 2022)

“The study shows that low-touch diversion programs like Philadelphia’s Accelerated Misdemeanor Program (AMP) can increase clean-slate exits from the criminal justice system and reduce recidivism.”

Recidivism Analysis Research Brief: Community Justice Support Centers

University of Pennsylvania’s Crime and Justice Policy Lab (March 2022)

“Community Justice Support Centers (CJSCs) are an innovative, court-run initiative that combine traditional community monitoring with treatment, education, and career services to keep clients that are at high-risk for recidivism out of jail or prison. We analyzed court data to track outcomes of CJSC participants both before and after the significant program changes in 2016. Although this research is limited to retrospective data, three different types of analyses all suggest that current CJSCs are reducing rates of recidivism among participants.”

Reforming the Police Through Procedural Justice Training: A Multicity Randomized Trial at Crime Hot Spots

David Weisburd, Cody W. Telep , Heather Vovak , Taryn Zastrow , Anthony A. Braga, and Brandon Turchan (January 2022)

“The training led to increased knowledge about Procedural Justice (PJ) and more procedurally just behavior in the field as compared with the Standard Condition (SC) condition. At the same time, PJ officers made many fewer arrests than SC officers. Residents of the PJ hot spots were significantly less likely to perceive police as harassing or using unnecessary force, though we did not find significant differences between the PJ and SC hot spots in perceptions of PJ and police legitimacy. We found a significant relative 14% decline in crime incidents in the PJ hot spots during the experiment.”

Reducing crime by remediating vacant lots: the moderating effect of nearby land uses

John Macdonald, Viet Nguyen, Shane T. Jensen & Charles C. Branas (January 2021)

“Vacant lot greening was estimated to reduce total crime and multiple subcategories in both the quasi-experimental and experimental evaluations. Remediating vacant lots had a smaller effect on reducing crime when they were located nearby train stations and alcohol outlets. The crime reductions from vacant lot remediations were larger when they were located near areas of active businesses. There is some suggestive evidence that the effects of vacant lot greening are larger when located in neighborhoods with higher pre-intervention levels of social cohesion.”

Click here to learn more about the LandCare program.

Changing Places: The Science and Art of New Urban Planning

John MacDonald, Charles Branas, and Robert Stokes (October 2019)

“The design of every aspect of urban landscape fundamentally shapes the health and safety for the communities who live there. Research highlighted in Changing Places showcases evidence from field experiments, natural experiments, and quasi-experimental evaluations how places can be redesigned and remediated to improve well-being of populations.”

Effect of Remediating Blighted Vacant Land on Shootings: A Citywide Cluster Randomized Trial

Ruth Moyer, John M. MacDonald, Greg Ridgeway, and Charles C. Branas (August 2018)

“Remediating vacant land with inexpensive, scalable methods, including greening or minimal mowing and trash cleanup, significantly reduced shootings that result in serious injury or death.”

Click here to learn more about the LandCare program.

The association between urban trees and crime: Evidence from the spread of the emerald ash borer in Cincinnati

Michelle C.Kondo, SeungHoon Hana, Geoffrey H. Donovan, John M. MacDonald (July 2016)

“Our results suggest that invasive tree pests may be associated with social costs
worth considering when managing invasive species. By extension, healthy trees may provide significant social benefits.”

Public Safety through Private Action: An Economic Assessment of BIDS

Philip J. Cook, John MacDonald (May 2011)

“Private actions to avoid and prevent criminal victimisation and assist public law enforcement are vital inputs into the crime‐control process. One form of private action, the business improvement district (BID), appears particularly promising. A BID is a non‐profit organisation created by property owners to provide local public goods, usually including public safety. Our analysis of 30 Los Angeles BIDs demonstrates that the social benefits of BID expenditures on security are a large multiple (about 20) of the private expenditures. Crime displacement appears minimal. Crime reduction in the BID areas has been accompanied by a reduction in arrests, suggesting further savings.”

Click here to learn more about business improvement districts.