In County of Los Angeles v. Mendez, the U.S. Supreme Court rejected the "provocation rule." Under the provocation rule, police officers using otherwise reasonable force could still be liable for violating the Fourth Amendment if they committed a separate Fourth Amendment violation that led to the need to use force in the first place ("provoked" the need for force). The U.S. Supreme Court rejected the provocation rule, noting "its fundamental flaw is that it uses another constitutional violation to manufacture an excessive force claim where one would not otherwise exist."
While conducting a search, Los Angeles County officers entered a shack where Angel Mendez was sleeping, without knocking or announcing the entry. Mendez picked up a BB gun to help him stand up. Officers shot him in the leg when they saw the gun. The Ninth Circuit concluded the use of force was reasonable, but officers were still liable by the provocation rule because they entered the shack without a warrant, in violation of the Fourth Amendment. In rejecting the Ninth Circuit's decision, the U.S. Supreme Court established important support for law enforcement.