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

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∗∗ Homicides increased dramatically in Chicago in 2016. In 2015, 480 Chicago residents were killed. The next year, 754 were killed—274 additional homicide victims, tragically producing an extraordinary 58% in- crease 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 street stops is a strong candidate for the causal factor, particularly since the timing of the homicide spike so directly coincides with the decline. Regression analysis of the homicide spike and related shooting crimes identifies the street stop vari- able 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 ∗ Ronald N. Boyce Presidential Professor of Criminal Law and University Distinguished Professor of Law, S.J. Quinney College of Law at the University of Utah. ∗∗ Professor, Economics Department at the University of Utah. The authors thank Chuck Abernathy, Susan Bandes, Shima Baradaran Baughman, Jennifer Bishop-Jenkins, Patricia Cassell, Griffin Edwards, Jonah Gelbach, Erika George, Christy Lopez, Michael Maltz, Josh Marquis, Jason Mazzone, Ed Mogul, John Rapapport, Lawrence Rosenthal, Stephen Rushin, Wesley Skogan, Matt Tok- son, Sherry Towers, the readers of the Volokh Conspiracy blog (http://reason.com/volokh), and the participants in colloquia at the University of Utah S.J. Quinney College of Law, the University of Illinois College of Law, and the Illinois Academy of Criminology for helpful comments, and also Maryann Dennis, Chaunceton Bird, Valeri Craigle, Felicity Murphy, and Susan Snyder for excellent research assistance. The authors remain solely responsible for any errors. Although this Article was a collaborative effort, Cassell had initial responsibility for data collection and legal analysis, and Fowles had initial responsibility for statistical analysis. We appreciate the financial sup- port provided by the Albert and Elaine Borchard Fund for Faculty Excellence. We thank the Chicago Police Department, which helped us gather data for this Article. We also thank the University of Chicago Crime Lab, which released an informative report on gun violence in Chicago, which we used as one source of data for our analysis. 1581 1582 UNIVERSITY OF ILLINOIS LAW REVIEW [Vol. 2018 to identify any other plausible candidate that fits the data as well as the decline in stops. Our regression equations permit quantification of the costs of the decline in street stops. Because of fewer stops in 2016, it appears that (conservatively calculating) approximately 245 additional victims were killed and 1,108 additional shootings occurred in that year alone. And these tremendous costs are not evenly distributed, but rather are concen- trated among Chicago’s African-American and Hispanic communities. The most likely explanation for the fall in stops that appears to have triggered the homicide spike is a consent decree on the subject entered in- to by the American Civil Liberties Union (“ACLU”) with the Chicago Po- lice Department (“CPD”). Accordingly, modifications to that consent decree may be appropriate. More broadly, these findings shed important light on the ongoing national debate about stop and frisk policies. The fact that America’s “Second City” suffered so badly from a decline in street stops suggests that the arguably 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 police street stop activities may be truly lifesaving measures that must be considered as part of any effec- tive law enforcement response to gun violence. TABLE OF CONTENTS I. INTRODUCTION ......................................................................................1584 II. AN OVERVIEW OF THE 2016 CHICAGO HOMICIDE SPIKE .......................1586 III. THE DIMENSIONS AND TIMING OF THE HOMICIDE SPIKE ......................1589 A. Data Sets of Interest ......................................................................1590 B. Seasonal Adjustment of Homicide and Shooting Data ..................1592 C. Identifying the Existence and Timing of a Break Point .................1593 D. Did Chicago Homicides Really “Spike” in 2016? ........................1595 IV. CHANGES IN STOP AND FRISK AS A CAUSE OF THE HOMICIDE SPIKE ....1596 A. What the Causal Factor Needs to Explain ....................................1597 1. The Homicide Spike was Limited to Chicago .........................1597 2. The Chicago Spike was Largely Limited to Gun-Related Crimes ....................................................................................1600 B. Changes in Street Stop Policies in 2016 .......................................1601 1. The Decline in Street Stops in 2016 .......................................1602 2. The Linkage Between Declines in Street Stops and Gun Crimes ....................................................................................1604 3. The Experience of Other Cities and Declining Stop and Frisks. .....................................................................................1608 C. Regression Analysis of Chicago’s Decline in Street Stops and the Homicide Spike .................................................................1613 V. OTHER POSSIBLE CAUSES OF THE HOMICIDE SPIKE ..............................1618 No. 5] WHAT CAUSED THE 2016 CHICAGO HOMICIDE SPIKE? 1583 A. Other Plausible, but Ultimately Inadequate, Candidates for the Homicide Spike ..............................................................................1618 1. Release of the Laquan McDonald Shooting Video .................1619 2. The Federal Investigation of the CPD ...................................1625 3. Changes in Police Leadership ................................................1628 B. Other Highly Implausible Candidates for Explaining the Spike ...1630 1. Fractured Gang Leadership ...................................................1630 2. The Opioid Epidemic ..............................................................1632 3. Gun Control Laws ..................................................................1633 4. Educational and Social Spending ..........................................1637 5. Socio-Economic Factors. .......................................................1638 C. A Preliminary Peek at the 2017 Data ............................................1639 VI. MODEL SPECIFICATION OF THE REGRESSION EQUATIONS .....................1644 A. The Problem of Model Specification .............................................1644 B. Bayesian Model Averaging of the Regression Equations ..............1645 VII. QUANTIFICATION OF THE COSTS OF THE DECLINE IN STOP AND FRISKS. ...................................................................................................1647 A. Human Costs .................................................................................1647 B. Financial Costs ..............................................................................1650 VIII. THE DROP IN STREET STOPS AS AN “ACLU EFFECT” ...........................1651 A. The ACLU Consent Decree ...........................................................1652 B. Contemporaneous Reports of an “ACLU Effect” .........................1653 C. The ACLU Consent Decree Compared to Illinois Legislation ......1661 IX. POLICY IMPLICATIONS ...........................................................................1662 A. Reassessing the Benefits of Street Stops ........................................1663 B. Reassuring Minority Communities About the Value of Street Stops ......................................................................1665 C. More Engagement of Police in Implementing Reforms .................1670 D. Removing or at Least Simplifying the Investigative Stop Report ..1672 E. Relying on Body Cameras .............................................................1674 F. Researching Street Stop Issues ......................................................1676 X. CONCLUSION ..........................................................................................1677 1584 UNIVERSITY OF ILLINOIS LAW REVIEW [Vol. 2018 “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 re- cent 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 February 1, 2016 regarding the Chicago homicide spike.2

Load more