Evaluating the causal mechanisms to police legitimacy and compliance in the United States: An in-depth mixed-methods approach

Procedural justice theory states that when police treat people in a fair, respectful, and neutralmanner, individuals are more likely to perceive the police as legitimate and obey the law. Totest this perspective, researchers often use experimental vignettes that depict police-citizeninteractions and measure subsequent attitudes. However, it is not straightforward to determinecausal effects from these designs, as one must carefully assess whether the effect runsthrough the intended theoretical pathways in order to properly test the theory. This paperadvances beyond ‘traditional’ experimental designs to evaluate the pathways linking police-citizen interactions, attitudes, and behavioral intentions. The data consist of a representativesample of 2,003 adults residing in the United States using an online panel. We use a mixedmethods approach combining a pre-registered 3x2x2 experimental vignette depicting a trafficstop by police with follow-up closed- and open-ended questions, allowing respondents toexplain their reasoning. We found that the quality of treatment by police was statisticallyrelated to subsequent perceptions of police legitimacy, but not compliance. However, follow-up placebo tests and open-text responses revealed a number of confounding factors limitingthe strength of causal claims regarding procedural justice theory. Most notably, a number ofrespondents expressed that they would comply with the officer in the moment, even if theydisagree, out of fear of escalation and their own personal safety. Research using(quasi-)experimental designs should evaluate causal assumptions and mechanisms morerigorously when theory testing, and likewise incorporate methods that can better assess theseintermediate processes, such as open text responses and process tracing.