UC Berkeley

Many recent high-profile killings by law enforcement, including the killing of George Floyd, a 46-year-old Black man, on May 25, 2020, which led to large nationwide protests, have highlighted police violence as a critical public health problem in the United States (US).1 Each year, approximately 1,000 individuals are killed by law enforcement,2 and more than 80,000 are treated for nonfatal injuries caused by law enforcement in US emergency departments.3 Experiences of police violence are inequitably distributed across the US population, with historically marginalized communities bearing the brunt of the burden.4–6 Research also suggests that these incidents have health and social implications beyond physical injury, including adverse mental health outcomes and distrust in public safety institutions.7–9 While a growing body of literature – with more recent substantial contributions from public health researchers – has made meaningful contributions to our understanding of the distribution and determinants of police violence, gaps remain due to various methodological limitations and a strong focus on particular individual-level factors. Specifically, past work has often overadjusted for potential mediating factors and has heavily relied on law enforcement agency records, which are prone to bias due to inaccurate reporting by officers and limit inference beyond the jurisdictions studied.10–12 Additionally, existing research has often investigated police violence incidence aggregated across demographic characteristics or among a limited set of subgroups (e.g., men).

To build on prior work, this dissertation utilizes a large and diverse, population-based healthcare dataset of emergency department and inpatient hospital visits throughout California, from 2005-2017, to contribute to our understanding of experiences of police violence among marginalized groups. In particular, this work focuses on examining police violence among groups in which existing work has methodological limitations – specifically, individuals suffering from psychiatric disorder – and in which research has been limited – specifically, racially marginalized youth. Individuals with mental and substance use disorders are over-represented among police encounters and the criminal justice system;11,13 however, most existing studies have controlled for potential mediating factors (e.g., hostile behavior/resistance) and have not been able to distinguish between particular types of disorders due to reliance on agency records.14–17 Further, research assessing experiences of police violence among youth specifically is limited. Although encounters with law enforcement are less common at younger ages, experiences of police violence during childhood and adolescence may be particularly harmful, with potential acute and long-term adverse health implications.18–20 Taken together with the disproportionate policing of Black youth, there is a need for research to document experiences of police violence in young people’s lives.21,22

The first chapter provides background on police violence as a critical public health issue in the US and existing literature on the distribution and determinants of police violence. It also motivates the examination of the role of psychiatric disorders in police violence risk and of patterns of police violence among young people specifically. Chapters 2 and 3 examine the relationship between particular psychiatric disorders and nonfatal legal intervention injury among adults throughout California, using hospital discharge records from 2005-2014. Chapter 2 employs a cross-sectional design to assess the over-representation of specific disorders among nonfatal legal intervention injury cases compared to the general US adult population. This work finds that nonaffective psychoses, mood disorders, alcohol use disorders, and drug use disorders were substantially over-represented among adult nonfatal legal intervention injury cases, particularly those treated in inpatient settings, compared to the general population. Comparison of injury severity scores across legal intervention injury cases with and without the disorders studied suggests that the large prevalence differences observed among inpatient cases specifically may partially be explained by the selection of injury cases with disorders into the inpatient setting. Chapter 3 builds on these cross-sectional findings by presenting a cumulative case-control study to assess the relations between specific disorders and subsequent experiences of nonfatal legal intervention injury, both overall and by race/ethnicity, with careful consideration of confounder control to avoid overadjustment for potential mediating factors.23,24 Results from Chapter 3 show that having particular mental and/or substance use disorder diagnoses in the year prior was strongly associated with subsequent nonfatal legal intervention injury among adults. The strongest associations were observed for personality disorder, comorbid mental and substance use disorder, nonaffective psychosis, and bipolar disorder, and relations varied by race/ethnicity. Potential direct (i.e., disorder-associated symptoms directly increasing risk of encounter and/or injury) and indirect (e.g., poverty- and homelessness-mediated relation between disorders and injury) mechanisms for these relations are discussed.

Chapter 4, a descriptive study, assesses the patterning of legal intervention injuries among young people specifically, throughout California, from 2005 to 2017 – examining inequities at the intersections of age, sex, and race/ethnicity. Findings reveal stark inequities in injuries caused by law enforcement among youth. Specially, they show that Black boys and girls, as young as 10 years old, experience markedly higher rates of injuries caused by law enforcement compared to youth of other races/ethnicities, and that relative inequities are larger at younger ages. These findings lend support to police violence as a form of structural racism, acting through both inequitable exposures to the criminal legal system and harsher outcomes during encounters among Black youth.21,22,25 Chapter 5 provides overall conclusions, with discussion of the broader implications of findings and recommendations for future work. Overall, this work contributes epidemiologic evidence on the distributions and determinants of police violence, incorporating design and analytic approaches that overcome some of the limitations of existing research, and presents findings that may provide insight into potential points of intervention that can be leveraged to reduce incidents of police violence.