Believing that respondent was impersonating a police officer, petitioner Haner, a Washington State Patrol officer, pursued and pulled over respondent's vehicle. While questioning respondent at the scene, petitioner Devenpeck, Haner's supervisor, discovered that respondent was taping their conversation and arrested him for violating the State's Privacy Act. The state trial court subsequently dismissed the charge. Respondent then filed this suit in federal court, claiming, among other things, that his arrest violated the Fourth and Fourteenth Amendments. The District Court denied petitioners qualified immunity, and the case went to trial. The jury was instructed, inter alia, that respondent had to establish lack of probable cause to arrest, and that taping police at a traffic stop was not a crime in Washington. The jury found for petitioners. The Ninth Circuit reversed, based in part on its conclusion that petitioners could not have had probable cause to arrest. It rejected petitioners' claim that there was probable cause to arrest for impersonating and for obstructing a law enforcement officer, because those offenses were not "closely related" to the offense invoked by Devenpeck at the time of arrest.

Held:

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