Whether a free citizen's excessive-force claim arising during an arrest, investigatory stop, or other seizure is governed by substantive due process or by the Fourth Amendment.
Holding
Such a claim is governed by the Fourth Amendment's prohibition on unreasonable seizures, not by a generalized substantive-due-process standard.
Reasoning
Section 1983 does not itself create substantive rights; it supplies a remedy for violations of rights found elsewhere in federal law. A court therefore must first identify the particular constitutional right allegedly infringed rather than treat excessive force as violating a free-floating, generic constitutional right.
The Fourth Amendment expressly protects persons against unreasonable seizures. Because an arrest or investigatory stop of a free citizen is a seizure, force used to carry out that seizure must be evaluated under the Amendment's reasonableness requirement.
Tennessee v. Garner had already treated a claim involving deadly force used to apprehend a suspect as a Fourth Amendment question. Graham made explicit that the same framework applies to all force used in the course of an arrest, investigatory stop, or other seizure of a free citizen, whether deadly or nondeadly.
The Court distinguished other custodial settings. The Eighth Amendment supplies the principal protection for convicted prisoners challenging force as cruel and unusual punishment, while the Due Process Clause protects pretrial detainees from force amounting to punishment. But those standards do not displace the Fourth Amendment where the challenged force occurs during a seizure of a free citizen.