To read this content please select one of the options below:

Operation Thumbs Down: A quasi-experimental evaluation of an FBI gang takedown in South Central Los Angeles

Jerry H. Ratcliffe (Department of Criminal Justice, Temple University, Philadelphia, Pennsylvania, USA)
Amber Perenzin (Department of Criminal Justice, Temple University, Philadelphia, Pennsylvania, USA)
Evan T. Sorg (Department of Law and Justice Studies, Rowan University, Glassboro, New Jersey, USA)

Policing: An International Journal

ISSN: 1363-951X

Article publication date: 15 May 2017




The purpose of this paper is to evaluate the violence-reduction effects following an FBI-led gang takedown in South Central Los Angeles.


The time series impact of the intervention was estimated using a Bayesian diffusion-regression state-space model designed to infer a causal effect of an intervention using data from a similar (non-targeted) gang area as a control.


A statistically significant 22 percent reduction in violent crime was observed, a reduction that lasted at least nine months after the interdiction.

Research limitations/implications

The research method does make assumptions about the equivalency of the control area, though statistical checks are employed to confirm the control area crime rate trended similarly to the target area prior to the intervention.

Practical implications

The paper demonstrates a minimum nine-month benefit to a gang takedown in the target area, suggesting that relatively long-term benefits from focused law enforcement activity are possible.

Social implications

Longer-term crime reduction beyond just the day of the intervention can aid communities struggling with high crime and rampant gang activity.


Few FBI-led gang task force interventions have been studied for their crime reduction benefit at the neighborhood level. This study adds to that limited literature. It also introduces a methodology that can incorporate crime rates from a control area into the analysis, and overcome some limitations imposed by ARIMA modeling.



The authors would like to thank Shea Gibson, Eric Mayo, Rob Bornstein from the FBI, and Detective Cedric Washington from the LAPD for their assistance in this research. Funding for this research was generously provided by Federal Bureau of Investigation (FBI) contract A21200117. The views expressed in this paper are not necessarily those of the FBI or the Department of Justice.


Ratcliffe, J.H., Perenzin, A. and Sorg, E.T. (2017), "Operation Thumbs Down: A quasi-experimental evaluation of an FBI gang takedown in South Central Los Angeles", Policing: An International Journal, Vol. 40 No. 2, pp. 442-458.



Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited

Related articles