of a person does not invalidate a valid arrest is equally applicable to an officer's reasonable failure to appreciate that a valid warrant describes too broadly the premises to be searched. Under the reasoning in Hill, the validity of the search of respondent's apartment pursuant to a warrant authorizing the search of the entire third floor depends on whether the officers' failure to realize the overbreadth of the warrant was objectively understandable and reasonable. Here it unquestionably was. The objective facts available to the officers at the time suggested no distinction between McWebb's apartment and the third-floor premises.12

For that reason, the officers properly responded to the command contained in a valid warrant even if the warrant is interpreted as authorizing a search limited to McWebb's apartment rather than the entire third floor. Prior to the officers' discovery of the factual mistake, they perceived McWebb's apartment and the third-floor premises as one and the same; therefore their execution of the warrant reasonably included the entire third floor. 13 Under either interpretation of the warrant, the officers' conduct was consistent with a reasonable effort to ascertain and identify the place intended to be searched within the meaning of the Fourth Amend

12 Nothing McWebb did or said after he was detained outside 2036 Park Avenue would have suggested to the police that there were two apartments on the third floor. McWebb provided the key that opened the doors on the first floor and on the third floor. The police could reasonably have believed that McWebb was admitting them to an undivided apartment on the third floor. When the officers entered the foyer on the third floor, neither McWebb nor Garrison informed them that they lived in separate apartments. App. 39-40, 42.

13 We expressly distinguish the facts of this case from a situation in which the police know there are two apartments on a certain floor of a building, and have probable cause to believe that drugs are being sold out of that floor, but do not know in which of the two apartments the illegal transactions are taking place. A search pursuant to a warrant authorizing a search of the entire floor under those circumstances would present quite different issues from the ones before us in this case.

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ment.14 Cf. Steele v. United States, 267 U. S. 498, 503 (1925).

The judgment of the Court of Appeals is reversed, and the case is remanded for further proceedings not inconsistent with this opinion.

It is so ordered.

JUSTICE BLACKMUN, with whom JUSTICE BRENNAN and JUSTICE MARSHALL join, dissenting.

Under this Court's precedents, the search of respondent Garrison's apartment violated the Fourth Amendment. While executing a warrant specifically limited to McWebb's residence, the officers expanded their search to include re

"Respondent argued that the execution of the warrant violated the Fourth Amendment at the moment when the officers "walked in through that threshold of that house . . . ." Tr. of Oral Arg. 35. At another point respondent argued that the search was illegal at the point when the police went through Garrison's apartment without probable cause for his apartment. Id., at 43. For the purpose of addressing respondent's argument, the exact point at which he asserts the search became illegal is not essential. Whether the illegal threshold is viewed as the beginning of the entire premises or as the beginning of those premises that, upon closer examination, turn out to be excluded from the intended scope of the warrant, we cannot accept respondent's argument. It would brand as illegal the execution of any warrant in which, due to a mistake in fact, the premises intended to be searched vary from their description in the warrant. Yet in this case, in which the mistake in fact does not invalidate the warrant precisely because the police do not know of the mistake in fact when they apply for, receive, and prepare to execute the warrant, the police cannot reasonably know prior to their search that the warrant rests on a mistake in fact. It is only after the police begin to execute the warrant and set foot upon the described premises that they will discover the factual mistake and must reasonably limit their search accordingly.

Respondent proposes that the police conduct a preliminary survey of the premises whenever they search a building in which there are multiple dwelling units, in order to determine the extent of the premises to be searched. Id., at 42. We find no persuasive reason to impose such a burden over and above the bedrock requirement that, with the exceptions we have traced in our cases, the police may conduct searches only pursuant to a reasonably detailed warrant.

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480 U. S. spondent's adjacent apartment, an expansion made without a warrant and in the absence of exigent circumstances. In my view, Maryland's highest court correctly concluded that the trial judge should have granted respondent's motion to suppress the evidence seized as a result of this warrantless search of his apartment. Moreover, even if I were to accept the majority's analysis of this case as one involving a mistake on the part of the police officers, I would find that the officers' error, either in obtaining or in executing the warrant, was not reasonable under the circumstances.

I

The home always has received special protection in analysis under the Fourth Amendment, which protects the "right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures” (emphasis added). See Silverman v. United States, 365 U. S. 505, 511 (1961) (“At the very core [of the Fourth Amendment] stands the right of a man to retreat into his own home and there be free from unreasonable governmental intrusion"). The Fourth Amendment, in fact, was a direct response to the colonists' objection to searches of homes under general warrants or without warrants. See Chimel v. California, 395 U. S. 752, 761 (1969); Harris v. United States, 331 U. S. 145, 157-163 (1947) (Frankfurter, J., dissenting). In today's society, the protection of the Amendment of course is extended to the equivalent of the traditional singlefamily house, such as an apartment. See, e. g., Ker v. California, 374 U. S. 23, 42 (1963).

The Court has observed that, in determining whether one has an interest protected by the Fourth Amendment, it is appropriate not to limit the analysis to the place in question, for "the Fourth Amendment protects people-and not simply 'areas."" Katz v. United States, 389 U. S. 347, 353 (1967). As articulated by Justice Harlan in his Katz concurrence, the proper test under the Amendment is whether "a person [has]

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...

exhibited an actual (subjective) expectation of privacy that society is prepared to recognize as 'reasonable."" Id., at 361. Justice Harlan noted, however, that an answer to the question concerning what protection the Fourth Amendment gave to a particular person always “requires reference to a 'place."" Ibid. In his view, the home would meet this test in virtually all situations. "[A] man's home," he stated, “is, for most purposes, a place where he expects privacy.' Ibid. The home thus has continued to occupy its special role in Fourth Amendment analysis in the post-Katz era. See Payton v. New York, 445 U. S. 573, 585 (1980) (“[T]he ‘physical entry of the home is the chief evil against which the wording of the Fourth Amendment is directed,"" quoting United States v. United States District Court, 407 U. S. 297, 313 (1972)); United States v. Karo, 468 U. S. 705, 714-715 (1984) ("Searches and seizures inside a home without a warrant are presumptively unreasonable absent exigent circumstances"); California v. Carney, 471 U. S. 386, 407-408 (1985) (STEVENS, J., dissenting) ("These places [mobile homes] may be as spartan as a humble cottage when compared to the most majestic mansion ... but the highest and most legitimate expectations of privacy associated with these temporary abodes should command the respect of this Court"); see also Steagald v. United States, 451 U. S. 204, 211 (1981); Coolidge v. New Hampshire, 403 U. S. 443, 477-478 (1971).

The Fourth Amendment also states that "no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized" (emphasis added). The particularity-of-description requirement is satisfied where "the description is such that the officer with a search warrant can with reasonable effort ascertain and identify the place intended." Steele v. United States, 267 U. S. 498, 503 (1925). In applying this requirement to searches aimed at residences within multiunit buildings, such as the search in the present case, courts have declared invalid those

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480 U. S.

warrants that fail to describe the targeted unit with enough specificity to prevent a search of all the units. See, e. g., United States v. Higgins, 428 F. 2d 232 (CA7 1970); United States v. Votteller, 544 F. 2d 1355, 1362-1363 (CA6 1976). Courts have used different criteria to determine whether a warrant has identified a unit with sufficient particularity. See, e. g., United States v. Bedford, 519 F. 2d 650, 655 (CA3 1975) (by name of occupant of apartment), cert. denied, 424 U. S. 917 (1976); Haynes v. State, 475 S. W. 2d 739, 741 (Tex. Crim. App. 1971) (by directions on how to reach a particular room); see generally 2 W. LaFave, Search and Seizure §4.5, p. 79 (1978); Crais, Sufficiency of Description of Apartment or Room to be Searched in Multiple-Occupancy Structure, 11 A. L. R. 3d 1330, 1340-1341, §5 (1967 and Supp. 1986).

Applying the above principles to this case, I conclude that the search of respondent's apartment was improper. The words of the warrant were plain and distinctive: the warrant directed the officers to seize marijuana and drug paraphernalia on the person of McWebb and in McWebb's apartment, i. e., "on the premises known as 2036 Park Avenue third floor apartment." App. 9. As the Court of Appeals observed, this warrant specifically authorized a search only of McWebb's-not respondent's-residence. 303 Md. 385, 392, 494 A. 2d 193, 196 (1985). In its interpretation of the war

'In reaching its conclusion, the Court of Appeals relied upon a statement by the trial judge that, pursuant to the warrant, only "the third floor apartment of the Defendant McWebb" could be searched. App. 46; 303 Md., at 392, 494 A. 2d, at 196. The majority contends that this reliance was unjustified, for, in making his statement, the trial judge was doing nothing more than rejecting respondent's contention that the warrant was general. Ante, at 82-83, n. 4. I fail to see how the interpretation of the Court of Appeals is inconsistent with the majority's understanding of this statement. The trial judge could have been rejecting respondent's argument about a general warrant by observing that the warrant here was limited to a single apartment, McWebb's. Such a view of the trial judge's remark does not contradict his observation that, in procuring and executing