Thin Blue Lines

Kevin Lewis

June 02, 2023

The “war on cops,” retaliatory violence, and the murder of George Floyd
Michael Sierra-Arévalo, Justin Nix & Scott Mourtgos
Criminology, forthcoming 


The police murder of George Floyd sparked nationwide protests in the summer of 2020 and revived claims that public outcry over such high-profile police killings perpetuated a violent “war on cops.” Using data collected by the Gun Violence Archive (GVA) on firearm assaults of U.S. police officers, we use Bayesian structural time series (BSTS) modeling to empirically assess if and how patterns of firearm assault on police officers in the United States were influenced by the police murder of George Floyd. Our analysis finds that the murder of George Floyd was associated with a 3-week spike in firearm assaults on police, after which the trend in firearms assaults dropped to levels only slightly above that which were predicted by pre-Floyd data. We discuss potential explanations for these findings and consider their relevance to the contemporary discussion of a “war on cops,” violence, and officer safety.

Smoking gun? Linking gun ownership to crime victimization
Stephen Billings
Journal of Public Economics, June 2023 


Using linked individual data on concealed handgun permits (CHP), reported crimes and arrests, I examine the dynamics of gun-ownership and criminal victimization. I initially show that being male, Republican, older, born in-state and a recent crime victim increases the probability that an adult obtains a CHP. Having a CHP increases property crime victimization by 46% with the largest impact on having a firearm stolen. Individual CHP holders see no change in violent crime victimization thus dispelling any benefits in terms of protection. Obtaining a CHP has a small (2%) increase in total crime and a larger increase on violent crime using a gun (8%) within the CHP holders neighborhood. Results suggest stolen guns spillover to neighborhood crime which is an important component of the larger social costs of gun ownership.

Racial/Ethnic Diversity in Positions of Power in U.S. Law Enforcement: An Examination of Active Representation and Disparities in Vehicle Stops
John Shjarback
Race and Justice, forthcoming 


Increasing minority representation in law enforcement has long been viewed as a means of improving police-citizen relations. Yet, little scholarly attention has examined whether racial/ethnic diversity translates into desired outcomes. These studies largely measure the racial/ethnic composition of the agency in general -- not in positions of power where they are most likely to make an impact on department policy/practice (i.e., ‘active representation’). Using data from the 2016 Law Enforcement Management and Administrative Statistics (LEMAS) survey, the current study 1) provides an overview of Black and Hispanic representation in chief executive, mid-level management, and supervisory roles and 2) explores the impact that diversity in these positions has on racial/ethnic disparities in vehicle stops in Illinois and Missouri. Minority officers are more underrepresented in these positions of power compared to their composition in agencies in general, and higher levels of representation are not significantly associated with reductions in disparities in stops.

Fame through surprise: How fame-seeking mass shooters diversify their attacks
Rayan Succar et al.
Proceedings of the National Academy of Sciences, 16 May 2023 


Mass shootings are becoming more frequent in the United States, as we routinely learn from the media about attempts that have been prevented or tragedies that destroyed entire communities. To date, there has been limited understanding of the modus operandi of mass shooters, especially those who seek fame through their attacks. Here, we explore whether the attacks of these fame-seeking mass shooters were more surprising than those of others and clarify the link between fame and surprise in mass shootings. We assembled a dataset of 189 mass shootings from 1966 to 2021, integrating data from multiple sources. We categorized the incidents in terms of the targeted population and shooting location. We measured “surprisal” (often known as “Shannon information content”) with respect to these features, and we scored fame from Wikipedia traffic data -- a commonly used metric of fame. Surprisal was significantly higher for fame-seeking mass shooters than non-fame-seeking ones. We also registered a significant positive correlation between fame and surprisal controlling for the number of casualties and injured victims. Not only do we uncover a link between fame-seeking behavior and surprise in the attacks but also we demonstrate an association between the fame of a mass shooting and its surprise.

Contested Killings: The Mobilizing Effects of Community Contact with Police Violence
Kevin Morris & Kelsey Shoub
American Political Science Review, forthcoming 


Recently, we have witnessed the politicizing effects of police killings in the United States. This project asks how such killings might (de)mobilize voters at the local level. We draw on multiple theoretical approaches to develop a theory of community contact with the police. We argue that when a highly visible event tied to government actions occurs -- like a police killing -- it can spur turnout. This is especially true where public narratives tie such events to government and structural causes. By comparing neighborhoods near a killing before and after election day, we estimate the causal effect on turnout. We find a mobilizing effect. These effects are larger when they “trend” on Google, occur in Black communities, or if the victim is Black. Proximity to a killing also increases support for abolishing the police. We conclude that police violence increases electoral participation in communities where narratives about racially unjust policing resonate most.

Crime and Demand for Police
Michael Coury
State University of New York Working Paper, February 2023 


This paper studies how exposure to crime affects demand for policing using a unique setting where both crime and demand for police can be measured at the neighborhood level. I use precinct-level returns from ballot measures in San Francisco to provide novel evidence on how individuals’ support for pro-police policies responds to exposure to crime. Using variation in criminal activity across neighborhoods around election day, I find that each additional violent crime leads to an increase in support for police union-endorsed ballot positions ranging from 2.9 percentage points for homicides to 0.4 percentage points for lesser crimes. The effects are largest in neighborhoods with high shares of white residents.

On the Public Finance of Capital Punishment 
Alexander Lundberg
American Law and Economics Review, forthcoming 


This study examines how local governments handle the financial demands of capital trials. With longitudinal data on county expenditures in Texas, fixed-effects regression estimates underscore two fiscal impacts of capital trials. First, counties raise property tax rates by an average of one-half basis point in years with a concluded trial. Second, counties reduce public safety expenditure by an average of approximately one million dollars. These results are consistent with national, cross-sectional research.

Does Stable Employment after Prison Reduce Recidivism Irrespective of Prior Employment and Offending?
Simon Kolbeck, Steven Lopez & Paul Bellair
Justice Quarterly, forthcoming 


Sampson and Laub’s (1990, 1993) life course theory posits that stable employment can rehabilitate a criminal trajectory, irrespective of criminal history. Others contend that post-prison employment could be attributable to pre-prison patterns. These hypotheses have not been fully evaluated. Drawing on a random sample of 1,607 restored citizens in Ohio, this paper analyzes matched administrative and unemployment insurance (UI) data across three-year pre- and post-prison periods and provides new evidence that employment stability reduces recidivism irrespective of pre-prison employment stability or extensive criminal history. Individuals we label “employment gainers” lacked stable employment before prison, comprise 41% of the stably employed after prison, with recidivism levels indistinguishable from those with stable employment in both periods. Reductions in recidivism associated with employment stability are consistent across levels of criminal history. Our results thus carve a clearer vision of the possibilities for redemption among those with marginal employment histories and extensive criminal histories.

Rivalries, reputation, retaliation, and repetition: Testing plausible mechanisms for the contagion of violence between street gangs using relational event models 
Jason Gravel et al.
Network Science, June 2023, Pages 324-350 


The hypothesis that violence -- especially gang violence -- behaves like a contagious disease has grown in popularity in recent years. Scholars have long observed the tendency for violence to cluster in time and space, but little research has focused on empirically unpacking the mechanisms that make violence contagious. In the context of gang violence, retaliation is the prototypical mechanism to explain why violence begets violence. In this study, we leverage relational event models (REMs) -- an underutilized yet particularly well-suited modeling technique to study the dynamics of inter-gang violence. We use REMs to examine gang violence’s tendency to replicate -- for which retaliation is but one plausible mechanism -- and its tendency to diffuse to other groups. We rely on data on conflicts between gangs in a region of Los Angeles over 3 years. We consider how the characteristics of gangs, their spatial proximity, networks of established rivalries, and the evolving history, directionality, and structure of conflicts predict future inter-gang conflicts. While retaliation is an important mechanism for the replication of violence, established rivalries, and inertia -- a gang’s tendency to continue attacking the same group -- are more important drivers of future violence. We also find little evidence for an emerging pecking order or status hierarchy between gangs suggested by other scholars. However, we find that gangs are more likely to attack multiple gangs in quick succession. We propose that gang violence is more likely to diffuse to other groups because of the boost of internal group processes an initial attack provides.

Improving forensic perpetrator identification with Super-Recognizers
Maren Mayer & Meike Ramon
Proceedings of the National Academy of Sciences, 16 May 2023 


About a decade ago, Super-Recognizers (SRs) were first described as individuals with exceptional face identity processing abilities. Since then, various tests have been developed or adapted to assess individuals’ abilities and identify SRs. The extant literature suggests that SRs may be beneficial in police tasks requiring individual identification. However, in reality, the performance of SRs has never been examined using authentic forensic material. This not only limits the external validity of test procedures used to identify SRs, but also claims concerning their deployment in policing. Here, we report the first-ever investigation of SRs’ ability to identify perpetrators using authentic case material. We report the data of 73 SRs and 45 control participants. These include (a) performance on three challenging tests of face identity processing recommended by Ramon (2021) for SR identification; (b) performance for perpetrator identification using four CCTV sequences depicting five perpetrators and police line-ups created for criminal investigation purposes. Our findings demonstrate that the face identity processing tests used here are valid in measuring such abilities and identifying SRs. Moreover, SRs excel at perpetrator identification relative to control participants, with more correct perpetrator identifications, the better their performance across lab tests. These results provide external validity for the recently proposed diagnostic framework and its tests used for SR identification (Ramon, 2021). This study provides the first empirical evidence that SRs identified using these measures can be beneficial for forensic perpetrator identification. We discuss theoretical and practical implications for law enforcement, whose procedures can be improved via a human-centric approach centered around individuals with superior abilities.

The impact of alertness vs. fatigue on interrogators in an actigraphic study of field investigations
Zlatan Krizan et al.
Scientific Reports, April 2023 


Investigative interviews (e.g., interrogations) are a critical component of criminal, military, and civil investigations. However, how levels of alertness (vs. sleepiness) of the interviewer impact outcomes of actual interviews is unknown. To this end, the current study tracked daily fluctuations in alertness among professional criminal investigators to predict their daily experiences with actual field interviews. Fifty law-enforcement investigators wore a sleep-activity tracker for two weeks while keeping a daily-diary of investigative interviews conducted in the field. For each interview, the investigators indicated how well they established rapport with the subject, how much resistance they encountered, how well they maintained their own focus and composure, and the overall utility of intelligence obtained. Daily alertness was biomathematically modeled from actigraphic sleep duration and continuity estimates and used to predict interview characteristics. Investigators consistently reported more difficulties maintaining their focus and composure as well as encountering more subject resistance during interviews on days with lower alertness. Better interview outcomes were also reported on days with subjectively better sleep, while findings were generally robust to inclusion of covariates. The findings implicate adequate sleep as a modifiable fitness factor for collectors of human intelligence.

Segregation and “Out-of-Placeness”: The Direct Effect of Neighborhood Racial Composition on Police Stops
Laura Schenker et al.
Political Research Quarterly, forthcoming 


Differential police conduct may be attributed both to residential racial segregation and more general discriminatory attitudes and policies. We draw upon ethnographic and other studies of everyday policing to propose that police, in the context of racially segregated neighborhoods, intensively surveil individuals who are “out of place” in terms of their race and the local geographical context in which they are found. We then use statistical evidence from the New York City Police Department to compare stops in different neighborhoods. We find that the NYPD indeed carries out “stops” that differentially target African Americans and Hispanics present in predominantly white precincts, with the degree of surveillance increasing as precincts become more white, and as stops become more generic and less about specific, identifiable crimes.


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