Patrolling the streets is a large element of law enforcement efforts in California. Officers routinely stop people walking down the street because they suspect them of a crime. They might interrogate the pedestrian and even pat them down.
Without laws that limit how evidence uncovered during this kind of police stop can be used in court, the possibility of police abusing their authority would be great. We could all be subject to random searches every time we set foot in public.
Perhaps the most important case the U.S. Supreme Court decided on the issue of police stop-and-frisk incidents is titled Terry v. Ohio. It is a 1968 decision, in which the Court set up rules governing when an officer can detain a suspect in the street without a warrant. Failure to abide by these rules makes any evidence uncovered during the search inadmissible if the suspect later faces criminal charges.
In the underlying case, an officer observed the defendant and two other men acting suspiciously near a store. He followed them a short distance, approached them and identified himself as an officer. After asking the men their names, he grabbed the defendant, spun him around and frisked him. He felt something that seemed to be a gun, and ordered the three men inside a nearby store. There, he uncovered a gun inside the defendant’s coat, as well as a second gun on one of the other men.
One of the main questions before the Supreme Court was: did the Fourth Amendment’s protection against unreasonable searches and seizures apply when the suspect was out in public? The justices ruled that it did.
Though stopping a person on the street is not the same as a formal arrest, the Court found, since the suspect cannot walk away, he or she has been “seized” for the purposes of the Fourth Amendment.
The Court ruled that, in order for a police stop to be legal, the officer must have a reasonable suspicion that the suspect has committed a crime, is committing one, or is about to. Lacking that, anything the officer uncovers during a subsequent pat-down is tainted by the illegality of the search, and cannot be sued in court.