Illinois v. Rodriguez, 497 U.S. 177 (1990)
Syllabus
Respondent was arrested in his apartment and charged with possession of illegal drugs, which the police had observed in plain view and seized. The officers did not have an arrest or search warrant, but gained entry to the apartment with the assistance of Gail Fischer, who represented that the apartment was “our[s]” and that she had clothes and furniture there, unlocked the door with her key, and gave the officers permission to enter. The trial court granted respondent’s motion to suppress the seized evidence, holding that at the time she consented to the entry Fischer did not have common authority because she had moved out of the apartment. The court also rejected the State’s contention that, even if Fischer did not have common authority, there was no Fourth Amendment violation if the police reasonably believed at the time of their entry that she possessed the authority to consent. The Appellate Court of Illinois affirmed.
Held:
1. The record demonstrates that the State has not satisfied its burden of proving that Fischer had “joint access or control for most purposes” over respondent’s apartment, as is required under United States v. Matlock, 415 U. S. 164,  415 U. S. 171, n. 7, to establish “common authority.” Pp.  497 U. S. 181-182.
2. A warrantless entry is valid when based upon the consent of a third party whom the police, at the time of the entry, reasonably believe to possess common authority over the premises, but who in fact does not. Pp. 497 U. S. 182-189.
(a) Because the Appellate Court’s opinion does not contain a “plain statement” that its decision rests on an adequate and independent state ground, it is subject to review by this Court.  See Michigan v. Long, 463 U. S. 1032,  463 U. S. 1040-1042. P.  497 U. S. 182.
(b) What respondent is assured by the Fourth Amendment is not that no government search of his house will occur unless he consents; but that no such search will occur that is “unreasonable.” As with the many other factual determinations that must regularly be made by government agents in the Fourth Amendment context, the “reasonableness” of a police determination of consent to enter must be judged not by whether the police were correct in their assessment, but by the objective
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standard of whether the facts available at the moment would warrant a person of reasonable caution in the belief that the consenting party had authority over the premises. If not, then warrantless entry without further inquiry is unlawful unless authority actually exists. But if so, the search is valid.  Stoner v. California,376 U. S. 483 reconciled. Pp.  497 U. S. 183-189.
(c) On remand, the appellate court must determine whether the police reasonably believed that Fischer had authority to consent to the entry into respondent’s apartment. P.  497 U. S. 189.
177 Ill.App.3d 1154, 140 Ill.Dec. 583, 550 N.E.2d 65 (1989), reversed and remanded.
SCALIA, J., delivered the opinion of the Court, in which REHNQUIST, C.J., and WHITE, BLACKMUN, O’CONNOR, and KENNEDY, JJ., joined. MARSHALL, J., filed a dissenting opinion, in which BRENNAN and STEVENS, JJ., joined, post, p.  497 U. S. 189.Â
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