Black and unarmed: statistical interaction between age, perceived mental illness, and geographic region among males fatally shot by police using case-only design

Abstract

Purpose: We examine whether the race and armed status interact to modify the risk of being fatally shot by police within categories of civilian age and mental illness status, and U.S. region.

Methods: Data are from The Washington Post online public-use database of all U.S. police-involved shooting deaths. The sample includes black and white males with known armed status who were killed from 1/1/2015 through 12/31/2019 (n = 3090). A case-only design is used to assess multiplicative interaction using adjusted logistic regression.

Results: The fully adjusted interaction estimate is null (S_OR = 0.75; 95% confidence interval [CI] = 0.55-1.04). However, adjusted estimates within strata show that the risk of being armed versus unarmed when fatally shot is smaller for black than white males older than 54 years (S_OR = 0.18; 95% CI = 0.06-0.65), those showing mental illness signs (S_OR = 0.50; 95% CI = 0.26-0.98), and those killed in the South (S_OR = 0.52; 95% CI = 0.33-0.83), and that the risk is greater in the Midwest (S_OR = 2.42; 95% CI = 1.11-5.26). Notably, there is no black-white difference in armed status among younger age groups (S_OR≈0.89).

Conclusion: The race and armed status may interact leaving black males at a higher risk of being unarmed than white males when fatally shot by police among those older than 54 years, mentally impaired, and residing in the South. Causal interaction suggests a lower risk for unarmed blacks in the Midwest. Researchers should further explore the utility of the case-only design to study social-environmental interaction.

Keywords: African Americans; Case-control studies; Epidemiologic research design; Geographic location; Law enforcement; Mentally ill persons; Police.

Figure A.1.

Conceptual framework representing working knowledge of factors linking a civilian’s armed status and being shot and killed by police. Civilian behavior and situational factors were identified as mediators. Therefore, civilian socioeconomic status, demographics, and mental health status were assessed for confounding the association between being armed, shot and killed by police.

Figure 1.

The Washington Post (Wapo) study sample selection process.

Figure 2.

WaPo racial distribution of armed males killed annually by police.

Figure 3.

WaPo racial distribution of unarmed males killed annually by police.

Figure 4.

Fully-adjusted interaction estimate from Model 5 in Table 2 of the risk of being armed versus unarmed for Black compared to White males fatally shot by police 2015–19 in WaPo, and adjusted interaction estimates stratified by age, SMI status, and US region, where entries [CI] are main effects from case-only statistical Equation B which estimate the interaction term in statistical Equation A, assuming independence (N=3,090).