Groups – Ridgeway, Grogger, et al. (2019)

Study Reference:

Ridgeway, G., Grogger, J., Moyer, R. A., & Macdonald, J. M. (2019). Effect of gang injunctions on crime: A study of Los Angeles from 1988–2014. Journal of Quantitative Criminology, 35(3), 517-541.

Location in the Matrix; Methodological Rigor; Outcome:

Groups, Focused, Proactive; Rigorous; Effective

What police practice or strategy was examined?

Gang injunctions, a form of civil abatement order, were sought by the city attorney for areas where gang activity could be classified as constituting a public nuisance. These injunctions impose restrictions on gang members’ activities within defined geographic areas. They include naming specific gang members and lowering the standard of proof needed to stop and question known or suspected gang members within the area covered by the injunction. Police presence increased in these areas to enforce the injunctions. Forty-six gang injunctions existed in Los Angeles throughout the study period.

How was the intervention evaluated?

Quarterly crime data for the city were collected from 1988 to 2014, covering the implementation of gang injunctions in the city. Area designations in the city were coded as either part of an injunction area, adjacent to an injunction area, or not impacted. Time data on the start and endpoints for each gang injunction were also collected and overlaid with the area designations to analyze crime trends before, after, and during the enforcement of the gang injunctions. The analysis created an estimate of crime prevention using measures for short term effects (defined as 5 years), long term effects (defined as 27 years), and interruption effects (for three injunctions that were temporarily halted) on UCR Part I crime.

What were the key findings?

Gang injunctions were estimated to reduce total reported crime by 5% in the short term (5 years), and 18% over the long term (27 years). A reduction in assaults was the primary driver of the reduction in crime overall with a 19% reduction in assaults in the short term and 35% reduction in the long term. No displacement effect was detected.

What were the implications for law enforcement?

These findings indicate that gang injunctions serve as an effective strategy for localities to reduce gang violence and reduce overall crime in the area. The results also indicate that these crime prevention results grow over time after the injunctions have been in place and that localities need long-term commitments to seeking and enforcing the injunctions. Agencies should note that the strategy does involve civil liberty concerns arising from lowering the standard for stops of known or suspected gang members in the area.

Where can I find more information about this intervention, similar types of intervention, or related studies?