SJ Quinney College of Law, University of Utah Utah Law Digital Commons Utah Law Faculty Scholarship Utah Law Scholarship 3-2018 What Caused the 2016 Chicago Homicide Spike? An Empirical Examination of the 'ACLU Effect' and the Role of Stop and Frisks in Preventing Gun Violence Paul Cassell S.J. Quinney College of Law, University of Utah, [email protected] Richard Fowles Department of Economics, University of Utah Follow this and additional works at: https://dc.law.utah.edu/scholarship Part of the Criminal Law Commons, Criminal Procedure Commons, Fourth Amendment Commons, and the Human Rights Law Commons Recommended Citation Cassell, Paul and Fowles, Richard, "What Caused the 2016 Chicago Homicide Spike? An Empirical Examination of the 'ACLU Effect' and the Role of Stop and Frisks in Preventing Gun Violence" (2018). Utah Law Faculty Scholarship. 95. https://dc.law.utah.edu/scholarship/95 This Article is brought to you for free and open access by the Utah Law Scholarship at Utah Law Digital Commons. It has been accepted for inclusion in Utah Law Faculty Scholarship by an authorized administrator of Utah Law Digital Commons. For more information, please contact [email protected]. DRAFT OF APRIL 2, 2018 WHAT CAUSED THE 2016 CHICAGO HOMICIDE SPIKE? AN EMPIRICAL EXAMINATION OF THE “ACLU EFFECT” AND THE ROLE OF STOP AND FRISKS IN PREVENTING GUN VIOLENCE Paul G. Cassell & Richard Fowles ABSTRACT Homicides increased dramatically in Chicago in 2016. In 2015, 480 Chicago residents were killed. The next year, 754 were killed–274 more homicide victims, tragically producing an extraordinary 58% increase in a single year. This article attempts to unravel what happened. This article provides empirical evidence that the reduction in stop and frisks by the Chicago Police Department beginning around December 2015 was responsible for the homicide spike that started immediately thereafter. The sharp decline in the number of stop and frisks is a strong candidate for the causal factor, particularly since the timing of the homicide spike so perfectly coincides with the decline. Regression analysis of the homicide spike and related shooting crimes identifies the stop and frisk variable as the likely cause. The results are highly statistically significant and robust over a large number of alternative specifications. And a qualitative review for possible “omitted variables” in the regression equations fails to identify any other plausible candidates that fits the data as well as the decline in stop and frisks. Our regression equations permit quantification of the costs of the decline in stop and frisks. Because of fewer stop and frisks in 2016, it appears that (conservatively calculating) approximately 236 additional victims were killed and 1115 additional shootings occurred in that year alone. And these tremendous costs are not evenly distributed, but rather are concentrated among Chicago’s African-American and Hispanic communities. The most likely explanation for the fall in stop and frisks that appears to have triggered the homicide spike is a consent decree entered into by the American Civil Liberties Union (ACLU) with the Chicago Police Department (CPD). Accordingly, modifications to that consent decree may be appropriate. More broadly, these findings shed important light on the on-going national debate about stop and frisk policies. The fact that America’s “Second City” suffered so badly from a decline in stop and frisks suggests that the arguably i contrary experience in New York City may be an anomaly. The costs of crime— and particularly gun crimes—are too significant to avoid considering every possible measure for reducing the toll. The evidence gathered here suggests that stop and frisk policies may be truly lifesaving measures that have to be considered as part of any effective law enforcement response to gun violence. TABLE OF CONTENTS I. INTRODUCTION ...................................................................................................... 2 II. AN OVERVIEW OF THE 2016 CHICAGO HOMICIDE SPIKE ................................... 4 III. THE DIMENSIONS AND TIMING OF THE HOMICIDE SPIKE .................................. 7 A. Data Sets of Interest ........................................................................................ 7 B. Seasonal Adjustment of Homicide and Shooting Data .................................. 11 C. Identifying the Existence and Timing of a Break Point ................................. 12 IV. CHANGES IN STOP AND FRISK AS A CAUSE OF THE HOMICIDE SPIKE ............. 14 A. What the Causal Factor Needs to Explain .................................................... 14 1. The Homicide Spike was Limited to Chicago ............................................ 14 2. The Chicago Spike was Largely Limited to Gun-Related Crimes .............. 17 B. Changes in Stop and Frisk Policies in 2016 ................................................. 19 1. The Decline in Stop and Frisks in 2016 ..................................................... 19 2. The Linkage Between Declines in Stop and Frisks and Gun Crimes ......... 21 3. The Experience of Other Cities and Declining Stop and Frisks. ............... 26 C. Regression Analysis of Chicago’s Decline in Stop and Frisks and the Homicide Spike ................................................................................................... 31 V. OTHER POSSIBLE CAUSES OF THE HOMICIDE SPIKE ......................................... 36 A. Other Plausible, But Ultimately Inadequate, Candidates for the Homicide Spike .................................................................................................................... 36 1. Release of the Laquan McDonald Shooting Video .................................... 37 2. The Federal Investigation of the Chicago Police Department .................. 43 3. Changes in Police Leadership ................................................................... 46 B. Other Highly Implausible Candidates for Explaining the Spike .................... 48 1. Fractured Gang Leadership ....................................................................... 48 2. The Opioid Epidemic .................................................................................. 50 3. Gun Control Laws ...................................................................................... 51 4. Educational and Social Spending .............................................................. 53 5. Socio-Economic Factors. ........................................................................... 55 C. A Preliminary Peek at the 2017 Data ........................................................... 55 VI. MODEL SPECIFICATION OF THE REGRESSION EQUATIONS .............................. 58 A. The Problem of Model Specification ............................................................. 59 B. Bayesian Model Averaging of the Regression Equations ............................. 60 VII. QUANTIFICATION OF THE COSTS OF THE DECLINE IN STOP AND FRISKS. ...... 62 A. Human Costs ................................................................................................. 63 B. Financial Costs .............................................................................................. 64 ii VIII. THE DROP IN STOP AND FRISKS AS AN “ACLU EFFECT” ............................. 65 A. The ACLU Consent Decree .......................................................................... 66 B. Contemporaneous Reports of an “ACLU Effect” .......................................... 68 C. The ACLU Consent Decree Compared to Illinois Legislation ....................... 74 IX. POLICY IMPLICATIONS ..................................................................................... 76 A. Reassessing the Benefits of Stop and Frisk .................................................... 76 B. Reassuring Minority Communities about the Value of Stop and Frisk .......... 79 C. Removing or at Least Simplifying the Investigative Stop Report .................. 84 D. Relying on Body Cameras ............................................................................. 87 E. Researching Stop and Frisk Questions ......................................................... 89 CONCLUSION .......................................................................................................... 90 APPENDIX A: THE 2016 CHICAGO HOMICIDE VICTIMS .......................................... 92 APPENDIX B: THE CHICAGO INVESTIGATIVE STOP REPORT .................................. 96 APPENDIX C: THE CHICAGO INVESTIGATIVE STOP RECEIPT ................................. 99 iii WHAT CAUSED THE 2016 CHICAGO HOMICIDE SPIKE? AN EMPIRICAL EXAMINATION OF THE “ACLU EFFECT” AND THE ROLE OF STOP AND FRISKS IN PREVENTING GUN VIOLENCE Paul G. Cassell∗ & Richard Fowles∗∗ “So by January 2016, the city was on fire. Cops had to worry about the ACLU deal. And many of them became scared and demoralized. So cops stopped making stops. And kids started shooting more – because they could, and because the rule of law, law enforcement, had been delegitimized. And that created an atmosphere of chaos.” —Letter from Chicago U.S. Attorney Zachary Fardon, upon his resignation in March 2017.1 “We reject any suggestion of a so-called ‘ACLU effect’ to explain the recent spike in gun violence on Chicago's streets. There is no discernible link between the rate of invasive street stops and searches by police and the level of violence. There simply is not any evidence of this so-called ‘effect.’” —Public letter from the Illinois ACLU on