Quantifying Gang Retaliation and the Impact of Incident Response 

• In Event: The Gang Reduction and Youth Development (GRYD) Program in the City of Los Angeles 

Abstract

Retaliation plays a central role in gang violence. It stands to reason, therefore, that strategies that seek to disrupt retaliation by mediating conflict following gang shootings and homicides should reduce the overall rate of gang violent crime.  Attempts to document such effects have shown mixed results in comparisons with statistically matched control areas.  We take a novel approach to the problem by seeking to model the dynamics of gang violence at the scale of individual events.  We use the model in an analysis of the Los Angeles Gang Reduction and Youth Development incident response (GRYD-IR) program.  A key observation is that retaliatory crimes need to be distinguished from gang crimes that arise spontaneously at a constant background rate.  With this distinction, the model is capable of discriminating between the impact of police, when operating alone, and the added effects of GRYD-IR.  Overall, GRYD-IR cuts the number of retaliations in half.  Estimates for the number of prevented aggravated assaults and homicides with attendant savings are presented.  

Authors

• Jeffrey Brantingham, University of California, Los Angeles

• Baichuan Yuan, UCLA, Department of Mathematics

• Nick Sundback, UCLA

• Denise Herz, California State University Los Angeles

• Kristine Chan, California State University Los Angeles