In 1968 a case called Terry v. Ohio took place. This case made a big impact on the police departments of the United States by giving officers more reasons to make an arrest. A "Terry Stop" is a stop of a person by law enforcement officers based upon reasonable suspicion that a person may have been engaged in criminal activity, whereas an arrest requires probable cause that a suspect committed a criminal offense.
A Cleveland detective (McFadden), on a downtown beat which he had been patrolling for many years, observed two stranger on a street corner. He saw them proceed alternately back and forth along an identical route, pausing to stare in the same store window, which they did for a total of about 24 times. Each completion of the route was followed by a conference between the two on a corner, at one of which they were joined by a third man who left swiftly. Suspecting the two men of "casing a job, a stick-up," the officer followed them and saw them rejoin the third man a couple of blocks away in front of a store. The officer approached the three, identified himself as a policeman, and asked their names. The men "mumbled something," whereupon McFadden spun petitioner around, patted down his outside clothing, and found in his overcoat pocket, but was unable to remove, a pistol. The officer ordered the three into the store. He removed petitioner's overcoat, took out a revolver, and ordered the three to face the wall with their hands raised. He patted down the outer clothing of Chilton and Katz and seized a revolver from Chilton's outside overcoat pocket. He did not put his hands under the outer garments of Katz (since he discovered nothing in his pat-down which might have been a weapon), or under petitioner's or Chilton's outer garments until he felt the guns. The three were taken to the police station. Petitioner and Chilton were charged with carrying concealed weapons.