Abstract: When people die in police custody, civil claims under 42 U.S.C. § 1983 alleging excessive force often follow, as affected families seek to hold state actors accountable for the deaths of their loved ones. In defending these claims, attorneys for law enforcement defendants have increasingly sought to avoid legal liability not merely by arguing that state actors were either acting reasonably or were immune from civil liability, but that police conduct simply did not cause death in the first place. While manufacturing doubt about cause of death has emerged as a central defense strategy in excessive force litigation, attention to disputes about causation have received virtually no scholarly attention, unlike more familiar elements of Fourth Amendment claims, like reasonableness and qualified immunity.
This Article provides the first comprehensive empirical study of causation disputes in Fourth Amendment excessive force cases, analyzing over 500 litigation documents from more than 200 in-custody death cases spanning nearly 50 years. The findings reveal three critical insights. First, what this Article terms “the causation defense” emerges abruptly in the late 1990s. Before 1997, causation disputes arose in only a small minority of cases; after 1997, they became a standard element of defense strategy. This shift was not accidental but rather was the product of defense oriented medical research designed to manufacture doubt about police responsibility for in custody deaths. Second, causation defenses fundamentally reshape Fourth Amendment doctrine. Courts convert causation arguments into reasonableness analysis, treating alternative possible causes of death as proof that death was unforeseeable and therefore that the force applied was reasonable. Expert testimony claiming tactics are generally “safe” leads courts to reject deadly force classification even in fatal cases. Third, courts systematically ignore a fundamental tort principle: that defendants must take plaintiffs as they find them. Police point to victims’ preexisting vulnerabilities — the very traits defendants invoke to as the true cause of death — as reasons to avoid liability.
This Article demonstrates that causation functions as a shadow immunity doctrine in excessive force litigation. It calls for courts to apply the principle that defendants take victims as they find them and scrutinize expert testimony more rigorously, while recognizing that doctrinal reforms alone cannot address a deeper effect of the causation defense: extending a long history of pathologizing victims of police violence and obscuring basic questions about state power.
