543 U.S. 146 (2004)
On the night of November 22, 1997, respondent Jerome Alford pulled his car off State Route 16 in Pierce County, Washington, behind a disabled vehicle and activated his wig-wag headlights while assisting the motorists with a flat tire.1 Officer Joi Haner of the Washington State Patrol passed the scene, turned around, and upon arrival learned from the motorists that Alford had given the impression of being a police officer through his statements and flashing lights, and had left his flashlight behind.2
Haner radioed his supervisor Sergeant Gerald Devenpeck expressing concern that Alford was an impersonator, then pursued and stopped Alford's vehicle.3 During the stop, Haner observed a police scanner tuned to the Kitsap County Sheriff’s Office frequency, handcuffs, and a hand-held scanner in the car, and found Alford's explanations about his prior law enforcement work and the headlights evasive and untruthful.4
Sergeant Devenpeck arrived shortly thereafter, questioned Alford about the headlights, noticed a tape recorder on the passenger seat with play and record buttons depressed, played the tape, and arrested Alford for violating the Washington Privacy Act by recording the conversation without consent.5 At booking, Alford was also ticketed for the flashing headlights, but both charges were later dismissed by the state trial court.6
Alford filed suit in federal district court against Haner and Devenpeck under 42 U.S.C. § 1983 and state law, alleging arrest without probable cause.7 The district court denied summary judgment on qualified immunity grounds.8 After trial the jury returned a verdict for the officers.9 A divided panel of the Ninth Circuit reversed.10 The Supreme Court granted certiorari.11
Whether an arrest is lawful under the Fourth Amendment when the criminal offense for which there is probable cause to arrest is not “closely related” to the offense stated by the arresting officer at the time of arrest?12
A warrantless arrest is reasonable under the Fourth Amendment where there is probable cause to believe that a criminal offense has been or is being committed.13 Whether probable cause exists depends upon the reasonable conclusion to be drawn from the facts known to the arresting officer at the time of the arrest.14 An arresting officer's state of mind is irrelevant to the existence of probable cause.15 The offense establishing probable cause need not be closely related to the offense identified by the arresting officer at the time of arrest.16
Yes. The established facts show that on November 22, 1997, Officer Haner learned from stranded motorists that Alford had activated wig-wag headlights and left the impression he was a police officer while assisting with a flat tire on State Route 16.17
Haner radioed Sergeant Devenpeck about his concern that Alford was an impersonator, then stopped Alford's vehicle and observed a police scanner, handcuffs, and evasive answers about prior law enforcement work and the headlights.18
Devenpeck arrived, discovered the tape recorder, and arrested Alford for violating the Washington Privacy Act.19 These facts known to the officers at the time supplied an objective basis for probable cause to believe Alford had committed impersonating an officer or obstructing a law-enforcement officer.20 The Fourth Amendment inquiry turns solely on the facts known to the officers and not on the offense they invoked or any requirement that it be closely related to another offense supported by those facts.21
The arrest is lawful under the Fourth Amendment when there is probable cause for an offense even if it is not closely related to the offense stated by the arresting officer at the time of arrest.22