The Endogenous Fourth Amendment: An Empirical Assessment of How Police Understandings of Excessive Force Become Constitutional Law

If the Fourth Amendment is designed to protect citizens from law enforcement abusing its powers, why are so many unarmed Americans killed? Traditional understandings of the Fourth Amendment suggest that it has an exogenous effect on police use of force, i.e., that the Fourth Amendment provides the ground rules for how and when law enforcement can use force that police departments turn into use-of-force policies that ostensibly limit police violence. In this Article, we ques- tion whether this exogenous understanding of the Fourth Amendment in relation to excessive force claims is accurate by engaging in an empirical assessment of the use-of-force poli- cies in the seventy-five largest American cities. We find that rather than translating Fourth Amendment standards into specific rules for police and clear protections for citizens in a “top down” fashion, use-of-force policies largely regurgitate the Fourth Amendment’s ambiguities concerning what is “reasonable” while inserting additional equivocations that reflect the interests of law enforcement. This empirical evidence, along with a doctrinal examination of how use-of-force policies are used when presented to federal courts, gives rise to a new understanding of the Fourth Amendment, where self-serving police understandings of excessive force are embedded in use- of-force policies and shape the meaning of reasonable force. These policies are often relied upon, referenced, or deferred to by federal courts as a lawful implementation of an ambiguous Fourth Amendment. Thus, rather than the Fourth Amendment having an exogenous effect on use-of-force policies and police behavior, this Article argues that federal courts often embrace an endogenous, or “bottom-up” meaning of excessive force where the policy preferences of police departments are rearticulated as constitutional law. This finding from our empirical work provides a new way to understand why use-of-force policies and the Fourth Amendment have been ineffective in combating excessive force by the police. Moreover, this endogenous understanding of Fourth Amendment excessive force jurisprudence opens up new avenues for legal reform.