Abstract

The concentration of police resources in stable crime hotspots has proven effective in reducing crime, but the extent to which police can disrupt dynamically changing crime hotspots is unknown. Police must be able to anticipate the future location of dynamic hotspots to disrupt them. Here we report results of two randomized controlled trials of near real-time epidemic-type aftershock sequence (ETAS) crime forecasting, one trial within three divisions of the Los Angeles Police Department and the other trial within two divisions of the Kent Police Department (United Kingdom). We investigate the extent to which (i) ETAS models of short-term crime risk outperform existing best practice of hotspot maps produced by dedicated crime analysts, (ii) police officers in the field can dynamically patrol predicted hotspots given limited resources, and (iii) crime can be reduced by predictive policing algorithms under realistic law enforcement resource constraints. While previous hotspot policing experiments fix treatment and control hotspots throughout the experimental period, we use a novel experimental design to allow treatment and control hotspots to change dynamically over the course of the experiment. Our results show that ETAS models predict 1.4–2.2 times as much crime compared to a dedicated crime analyst using existing criminal intelligence and hotspot mapping practice. Police patrols using ETAS forecasts led to an average 7.4% reduction in crime volume as a function of patrol time, whereas patrols based upon analyst predictions showed no significant effect. Dynamic police patrol in response to ETAS crime forecasts can disrupt opportunities for crime and lead to real crime reductions.

Additional information

Notes on contributors

G. O. Mohler

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

M. B. Short

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

Sean Malinowski

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

Mark Johnson

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

G. E. Tita

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

Andrea L. Bertozzi

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

P. J. Brantingham

G. O. Mohler is Assistant Professor, Department of Mathematics and Computer Science, Santa Clara University, Santa Clara, CA 95053 (E-mail: [email protected]). M. B. Short is Assistant Professor, School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332 (E-mail: [email protected]). Sean Malinowski is Commander and Chief of Staff, Los Angeles Police Department, Los Angeles, CA 90012 (E-mail: [email protected]). Mark Johnson is Head of Analysis, Kent Police Service, United Kingdom (E-mail: [email protected]). G. E. Tita is Professor, Department of Criminology, University of California, Irvine, Irvine, CA 92697 (E-mail: [email protected]). Andrea L. Bertozzi is Professor, Betsy Wood Knapp Chair for Innovation and Creativity, and Director of Applied Mathematics, Department of Mathematics, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). P. J. Brantingham, Department of Anthropology, University of California, Los Angeles, Los Angeles, CA 90095 (E-mail: [email protected]). This work was supported in part by NSF grant DMS-0968309, AFOSR MURI grant FA9550-10-1-0569, ONR grant N000141010221, ARO grant W911NF1010472, ARO MURI grant W911NF-11-1-0332, ONR grant N000141210838, ARO MURI grant W911NF-11-1-0332, and NSF Grant SES-1343123. Special thanks to Greg Ridgeway and Omar Qazi. GM and PJB are co-founders of PredPol, a company offering predictive policing services to law enforcement agencies. GM, PJB, MBS, ALB, and GET hold stock in PredPol.

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