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It is quite plain that the Fourth Amendment governs "seizures" of the person which do not eventuate in a trip to the stationhouse and prosecution for crime -- "arrests" in traditional terminology. It must be recognized that, whenever a police officer accosts an individual and restrains his freedom to walk away, he has "seized" that person. And it is nothing less than sheer torture of the English language to suggest that a careful exploration of the outer surfaces of a person's clothing all over his or her body in an attempt to find weapons is not a "search." Moreover, it is simply fantastic to urge that such a procedure [p17] performed in public by a policeman while the citizen stands helpless, perhaps facing a wall with his hands raised, is a "petty indignity." [n13] It is a serious intrusion upon the sanctity of the person, which may inflict great indignity and arouse strong resentment, and it is not to be undertaken lightly.
...
In this case, there can be no question, then, that Officer McFadden "seized" petitioner and subjected him to a "search" when he took hold of him and patted down the outer surfaces of his clothing.
We must decide whether, at that point, it was reasonable for Officer McFadden to have interfered with petitioner's personal security as he did. [n16] And, in determining whether the seizure and search were "unreasonable," our inquiry [p20] is a dual one -- 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.
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Nonetheless, the notions which underlie both the warrant procedure and the requirement of probable cause remain fully relevant in this context. In order to assess the reasonableness of Officer McFadden's conduct as a general proposition,
it is necessary "first to focus upon [p21] the governmental interest which allegedly justifies official intrusion upon the constitutionally protected interests of the private citizen," for there is
no ready test for determining reasonableness other than by balancing the need to search [or seize] against the invasion which the search [or seizure] entails.
...
The scheme of the Fourth Amendment becomes meaningful only when it is assured that, at some point, the conduct of those charged with enforcing the laws can be subjected to the more detached, neutral scrutiny of a judge who must evaluate the reasonableness of a particular search or seizure in light of the particular circumstances. [n19] And, in making that assessment, it is imperative that the facts be judged against an objective standard: would the facts [p22] available to the officer at the moment of the seizure or the search "warrant a man of reasonable caution in the belief" that the action taken was appropriate? Cf. Carroll v. United States, 267 U.S. 132 (1925); Beck v. Ohio, 379 U.S. 89, 96-97 (1964). [n20]
Anything less would invite intrusions upon constitutionally guaranteed rights based on nothing more substantial than inarticulate hunches, a result this Court has consistently refused to sanction. See, e.g., Beck v. Ohio, supra; Rios v. United States, 364 U.S. 253 (1960); Henry v. United States, 361 U.S. 98 (1959). And simple
"good faith on the part of the arresting officer is not enough." . . . If subjective good faith alone were the test, the protections of the Fourth Amendment would evaporate, and the people would be "secure in their persons, houses, papers, and effects," only in the discretion of the police.
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We merely hold today that, where a police officer observes
unusual conduct which leads him reasonably to conclude in light of his experience that criminal activity may be afoot and that the persons with whom he is dealing may be armed and presently dangerous, where, in the course of investigating this behavior, he identifies himself as a policeman and makes reasonable inquiries, and where nothing in the initial stages of the encounter serves to dispel his reasonable fear for his own or others' safety, he is entitled for the protection of himself and others in the area to conduct a carefully limited search of the outer clothing of such persons in an attempt to discover weapons which might be used to assault him. [p31] Such a search is a reasonable search under the Fourth Amendment, and any weapons seized may properly be introduced in evidence against the person from whom they were taken.
