Concept
The Terry Framework
Terry stop and frisk
The Terry Framework
The introduction left Detective McFadden watching from a store entrance 300 to 400 feet away, and the rest of Terry v. Ohio turns on what he did next.1 By his own account he had been a policeman for 39 years and a detective for 35, and he had patrolled that part of downtown for 30 years watching for shoplifters and pickpockets, so he read the pacing, the repeated peering into one window, and the conferring on the corner as preparation for a stickup.2 He approached the three men in front of the store, identified himself as a police officer, and asked their names. When they only mumbled, he grabbed Terry, spun him around, and patted down the outside of the overcoat, where he felt a pistol in the left breast pocket and removed a .38-caliber revolver.3 He then ordered the men into the store and frisked Chilton, who also carried a revolver, while the third man, Katz, had no weapon.4
Terry argued that without probable cause McFadden could neither seize him nor search him. The Court agreed that McFadden had done both, disagreed that either required probable cause, and held the pat-down a reasonable search, so the revolvers could be introduced as evidence.5 The holding has four working parts. The labels stop and frisk do not take police conduct outside the Fourth Amendment, a stop and a frisk each require their own justification, each intrusion is tested at its start and again for its scope, and a person who is only approached and questioned has not been stopped at all. The subsections below take those parts in that order.
Stop and Frisk as Seizure and Search
Before Terry, the Fourth Amendment's guarantee against unreasonable seizures of persons was analyzed in terms of arrest, and probable cause for arrest was treated as an absolute requirement.6 Against that background, a brief street detention looked like something outside the Amendment altogether, because the words stop and frisk suggest conduct too slight to count as a seizure or a search. The Court emphatically rejected that suggestion and held that the Amendment governs seizures of the person that never end in a trip to the station house, writing that "whenever a police officer accosts an individual and restrains his freedom to walk away, he has 'seized' that person."7 The same reasoning reaches the frisk, since exploring the outer surfaces of a person's clothing is a search.8
Treating a stop as a seizure did not mean requiring probable cause for it. As the Court later explained in Dunaway v. New York, Terry declined to stretch the concept of arrest to cover a brief on-the-spot stop and instead treated the stop and frisk as a special category of intrusion, so much less severe than an arrest that its reasonableness could be tested by balancing the limited invasion of privacy against the interests in preventing and detecting crime and in the officer's safety.9 The balance favors a lesser justification for a reason that comes from the nature of street work. In Adams v. Williams the Court observed that an officer who lacks probable cause need not shrug and allow a crime to occur, and that a brief stop to learn a person's identity or to hold the status quo while gathering information may be the most reasonable response.10 The intrusion is smaller than an arrest, so the required justification is smaller, but some justification must still exist.
The obvious objection is that a standard below probable cause hands officers a pretext for harassment. Terry's own answer was practical: the exclusionary rule does little to deter a frisk that an officer conducts purely for safety with no thought of prosecution, so a flat ban on stops and frisks would not stop police from continuing them.11 That answer places the real control at the front end, in the requirement that the officer be able to point to specific facts. No magistrate approves a street stop in advance, so a court can test it afterward only by asking what particular, observable facts the officer had when acting. Chief Justice Warren wrote that this demand for specificity in the information upon which police action is predicated "is the central teaching of this Court's Fourth Amendment jurisprudence."12
Two Separate Justifications
Terry attached two permissions to two different predicates, and the framework cannot be applied without keeping them apart. The first permission is the stop: an officer who has reasonable suspicion, supported by articulable facts, that a person is involved in criminal activity may briefly detain that person for investigation on less than probable cause.14 The second is the frisk: if the officer also reasonably suspects that the person is armed and presently dangerous, the officer may pat down the outer clothing for weapons.15 Later decisions describe the same pair as a brief stop with reasonable inquiries when criminal activity may be afoot, followed by a patdown when the officer is justified in believing that the person is armed and presently dangerous.16
Each permission has its own purpose, and the purposes explain why the second cannot ride on the first. The stop exists to give the officer time to inquire about possible criminal activity, so what it needs is suspicion about crime. The frisk exists to protect the officer while the inquiry goes on, so what it needs is suspicion about danger.17 The Court has described the purpose of the frisk as "not to discover evidence of crime, but to allow the officer to pursue his investigation without fear of violence."18 A frisk justified by the investigative purpose alone would have no limit, since any person suspected of any offense could be searched, and the safety purpose supplies the limit because it reaches only persons the officer has reason to fear are armed. The same logic runs the other way, so a lawful stop does not by itself authorize a frisk, because the facts that raise suspicion of a crime may say nothing about whether the person carries a weapon.19
McFadden's facts filled both boxes, though by different routes. The repeated pacing and conferring gave reasonable suspicion of a planned robbery, which supported the stop. His suspicion of a planned robbery was also the only ground he had for thinking Terry might be armed, and Justice Harlan's concurrence drew the practical conclusion that when the reason for the stop is an articulable suspicion of a crime of violence, the right to frisk may follow immediately and routinely, since an officer confronting a suspected robber should not have to ask a question and risk a bullet as the answer.20 That convenience belongs to cases in which the suspected crime itself signals danger, and later sections test the second box where it does not.
Justified at Inception, Limited in Scope
Satisfying the two predicates is necessary, and it ends the inquiry only for the start of each intrusion, because Terry also tests how the intrusion is carried out. The Court framed the test as a dual inquiry: whether the officer's action was "justified at its inception," and whether it was "reasonably related in scope to the circumstances which justified the interference in the first place."22 The first question looks only at what the officer knew when the intrusion began, so that what a search later turns up cannot retroactively justify it. A revolver found in an overcoat pocket says nothing about whether the officer had grounds before touching the coat.
The second question holds the intrusion to the reason that made it permissible. A stop justified by the need to inquire can last only as long as that inquiry reasonably requires, and a frisk justified by the fear of weapons is a carefully limited search of the outer clothing for weapons.23 The limit matters because Terry is an exception to the general rule that seizures rest on probable cause, and the Court has been careful to keep its scope narrow.24 If scope were left open, a stop supported by suspicion alone could grow into the full investigation that probable cause is supposed to gate, and the exception would swallow the rule.25 McFadden's pat-down illustrates the point: he began with the outside of the overcoat and removed the revolver after he felt it.26
The scope question has three recurring applications, each taken up later: whether a detention has become an arrest, whether it has lasted too long, and whether a pat-down has gone beyond the outer clothing for weapons. Each of them applies the same idea that an intrusion justified by a limited purpose may go only as far as that purpose reaches.
Encounters Versus Stops
Everything above applies only after the officer restrains the person. Police may approach people in public and ask questions without any justification, and the person approached may decline to cooperate and walk away. Justice White's separate opinion in Terry stated the point: the Constitution does not stop an officer from putting questions to anyone on the street, and absent special circumstances the person approached may not be detained or frisked but may decline to cooperate and walk away.28 Even a person who is properly detained is not obliged to answer, and a refusal to answer furnishes no basis for an arrest, though it may alert the officer to the need for continued observation.29
The line falls at restraint because the requirement of justification protects a person's freedom of movement. Questions that the person may decline leave that freedom intact, so nothing has been taken that needs a justification. A restraint removes the freedom, and from that moment the officer's authority must come from reasonable suspicion.30 The test therefore asks what the officer did to the person's ability to leave, and a courteous tone cannot turn a blocked sidewalk into a voluntary conversation.
Whether a seizure has occurred is therefore the first question in every street encounter, because a stop justification matters only once there is a stop to justify. The next section takes up how courts decide when that moment arrives.