Appeals concluded that the warrant did not authorize the search of respondent's apartment and the police had no justification for making a warrantless entry into his premises."

6

The opinion of the Maryland Court of Appeals relies on Article 26 of the Maryland Declaration of Rights and Maryland cases as well as the Fourth Amendment to the Federal Constitution and federal cases. Rather than containing any "plain statement" that the decision rests upon adequate and independent state grounds, see Michigan v. Long, 463 U. S. 1032, 1042 (1983), the opinion indicates that the Maryland constitutional provision is construed in pari materia with the

apartment of the Defendant McWebb"-was authorized by the warrant. The court then found on the precise facts of this case that the search of Garrison's apartment was valid because "the officers did not know that there was more than one apartment on the third floor and nothing alerted them of such a fact until after the search had been made and the items were [seized]." Id., at 46. The contrary construction adopted by the Court of Appeals fails to take into account the plain language of the warrant, which authorized a search of the person of McWebb and of the premises of 2036 Park Avenue, third floor. Id., at 9.

As the Court of Appeals explained:

"It is undisputed that the police were authorized to search only one apartment, McWebb's; the warrant did not authorize the search of Garrison's apartment. There is no question as to the validity of the search warrant itself. No argument was made in this Court that any of the exceptions to the warrant requirement applied here. It is clear, therefore, that the police had no authority to cross the threshold of Garrison's apartment and seize evidence.

“Police had a warrant to search McWebb's apartment. They had no warrant to search Garrison's. They had no justification for entering his premises, regardless of appearances." 303 Md. 385, 392-394, 494 A. 2d, 193, 196-197 (1985).

Article 26 of the Maryland Declaration of Rights provides:

"That all warrants, without oath or affirmation, to search suspected places, or to seize any person or property, are grevious [grievous] and oppressive; and all general warrants to search suspected places, or to apprehend suspected persons, without naming or describing the place, or the person in special, are illegal, and ought not to be granted."

Fourth Amendment.' We therefore have jurisdiction. Because the result that the Court of Appeals reached did not appear to be required by the Fourth Amendment, we granted certiorari. 475 U. S. 1009 (1986). We reverse.

In our view, the case presents two separate constitutional issues, one concerning the validity of the warrant and the other concerning the reasonableness of the manner in which it was executed. See Dalia v. United States, 441 U. S. 238, 258 (1979). We shall discuss the questions separately.

I

The Warrant Clause of the Fourth Amendment categorically prohibits the issuance of any warrant except one "particularly describing the place to be searched and the persons or things to be seized." The manifest purpose of this particularity requirement was to prevent general searches. By limiting the authorization to search to the specific areas and things for which there is probable cause to search, the requirement ensures that the search will be carefully tailored to its justifications, and will not take on the character of the wide-ranging exploratory searches the Framers intended to prohibit. Thus, the scope of a lawful search is "defined by the object of the search and the places in which there is probable cause to believe that it may be found. Just as probable cause to believe that a stolen lawnmower may be found in a garage will not support a warrant to search an upstairs bedroom, probable cause to believe that undocumented aliens are being transported in a van will not justify a warrantless

7303 Md., at 391, 494 A. 2d, at 196. This statement indicates that the "state court decision fairly appears to rest primarily on federal law, or to be interwoven with the federal law...." Michigan v. Long, 463 U. S., at 1040.

'See Andresen v. Maryland, 427 U. S. 463, 480 (1976); Stanley v. Georgia, 394 U. S. 557, 569-572 (1969) (Stewart, J., concurring in result); Stanford v. Texas, 379 U. S. 476, 481-482, 485 (1965); Go-Bart Importing Co. v. United States, 282 U. S. 344, 357 (1931); Marron v. United States, 275 U. S. 192, 195–196 (1927).

search of a suitcase." United States v. Ross, 456 U. S. 798, 824 (1982).

In this case there is no claim that the "persons or things to be seized" were inadequately described or that there was no probable cause to believe that those things might be found in "the place to be searched" as it was described in the warrant. With the benefit of hindsight, however, we now know that the description of that place was broader than appropriate because it was based on the mistaken belief that there was only one apartment on the third floor of the building at 2036 Park Avenue. The question is whether that factual mistake invalidated a warrant that undoubtedly would have been valid if it had reflected a completely accurate understanding of the building's floor plan.

Plainly, if the officers had known, or even if they should have known, that there were two separate dwelling units on the third floor of 2036 Park Avenue, they would have been obligated to exclude respondent's apartment from the scope of the requested warrant. But we must judge the constitutionality of their conduct in light of the information available to them at the time they acted. Those items of evidence that emerge after the warrant is issued have no bearing on whether or not a warrant was validly issued. Just as the discovery of contraband cannot validate a warrant invalid when issued, so is it equally clear that the discovery of facts demonstrating that a valid warrant was unnecessarily broad does not retroactively invalidate the warrant. The validity of the warrant must be assessed on the basis of the information that the officers disclosed, or had a duty to discover and to disclose, to the issuing Magistrate. 10 On the basis of that

'Cf. United States v. Jacobsen, 466 U. S. 109, 115 (1984) (warrantless test of white powder; "[t]he reasonableness of an official invasion of the citizen's privacy must be appraised on the basis of the facts as they existed at the time that invasion occurred”).

1o Arguments can certainly be made that the police in this case should have been able to ascertain that there was more than one apartment on the

information, we agree with the conclusion of all three Maryland courts that the warrant, insofar as it authorized a search that turned out to be ambiguous in scope, was valid when it issued.

II

The question whether the execution of the warrant violated respondent's constitutional right to be secure in his home is somewhat less clear. We have no difficulty concluding that the officers' entry into the third-floor common area was legal; they carried a warrant for those premises, and they were accompanied by McWebb, who provided the key that they used to open the door giving access to the thirdfloor common area. If the officers had known, or should have known, that the third floor contained two apartments before they entered the living quarters on the third floor, and thus had been aware of the error in the warrant, they would have been obligated to limit their search to McWebb's apart

third floor of this building. It contained seven separate dwelling units and it was surely possible that two of them might be on the third floor. But the record also establishes that Officer Marcus made specific inquiries to determine the identity of the occupants of the third-floor premises. The officer went to 2036 Park Avenue and found that it matched the description given by the informant: a three-story brick dwelling with the numerals 2-0-3-6 affixed to the front of the premises. App. 7. The officer "made a check with the Baltimore Gas and Electric Company and discovered that the premises of 2036 Park Ave. third floor was in the name of Lawrence McWebb." Ibid. Officer Marcus testified at the suppression hearing that he inquired of the Baltimore Gas and Electric Company in whose name the third floor apartment was listed: "I asked if there is a front or rear or middle room. They told me, one third floor was only listed to Lawrence McWebb." Id., at 36-38. The officer also discovered from a check with the Baltimore Police Department that the police records of Lawrence McWebb matched the address and physical description given by the informant. Id., at 7. The Maryland courts that are presumptively familiar with local conditions were unanimous in concluding that the officer reasonably believed McWebb was the only tenant on that floor. Because the evidence supports their conclusion, we accept that conclusion for the purpose of our decision.

ment. Moreover, as the officers recognized, they were required to discontinue the search of respondent's apartment as soon as they discovered that there were two separate units on the third floor and therefore were put on notice of the risk that they might be in a unit erroneously included within the terms of the warrant. The officers' conduct and the limits of the search were based on the information available as the search proceeded. While the purposes justifying a police search strictly limit the permissible extent of the search, the Court has also recognized the need to allow some latitude for honest mistakes that are made by officers in the dangerous and difficult process of making arrests and executing search warrants."1

In Hill v. California, 401 U. S. 797 (1971), we considered the validity of the arrest of a man named Miller based on the mistaken belief that he was Hill. The police had probable cause to arrest Hill and they in good faith believed that Miller was Hill when they found him in Hill's apartment. As we explained:

"The upshot was that the officers in good faith believed Miller was Hill and arrested him. They were quite wrong as it turned out, and subjective good-faith belief would not in itself justify either the arrest or the subsequent search. But sufficient probability, not certainty, is the touchstone of reasonableness under the Fourth Amendment and on the record before us the officers' mistake was understandable and the arrest a reasonable response to the situation facing them at the time." Id., at 803-804.

While Hill involved an arrest without a warrant, its underlying rationale that an officer's reasonable misidentification

""Because many situations which confront officers in the course of executing their duties are more or less ambiguous, room must be allowed for some mistakes on their part. But the mistakes must be those of reasonable men, acting on facts leading sensibly to their conclusions of probability." Brinegar v. United States, 338 U. S. 160, 176 (1949).