Whether one resident's voluntary consent makes a warrantless search of a shared home reasonable when another resident is physically present and expressly refuses consent.
Holding
No. As to the physically present resident who expressly refuses, a warrantless evidentiary search cannot be justified solely by another resident's consent.
Reasoning
The Fourth Amendment generally treats a warrantless entry into a home as unreasonable, subject to carefully drawn exceptions. Consent is one such exception. Under United States v. Matlock, a resident with common authority may consent to a search of shared premises when the other resident is absent, and Illinois v. Rodriguez permits reliance on reasonably apparent common authority. Neither precedent resolved a case in which a co-resident was at the door and directly objected.
Matlock rests not on technical property law, but on shared use, joint access, and social understandings about what co-inhabitants may authorize. A resident ordinarily assumes the risk that another resident may admit a visitor while the first resident is absent. But that ordinary assumption does not establish that one equal co-tenant has authority to override another equal co-tenant's contemporaneous objection.
Social expectations supplied the decisive point. A sensible visitor ordinarily would not enter a shared dwelling when one resident says to come in and another, standing there, says to stay out. Equal co-tenants may disagree about their shared space, but neither has a generally recognized superior authority to impose an invitation to an outsider over the other's express refusal.
The consenting resident's interests in reporting crime and distancing herself from suspected wrongdoing did not outweigh the objector's interest in the security of the home. A resident can give police information, turn over evidence on her own initiative, or provide facts supporting a warrant. The Fourth Amendment generally prefers those routes to a warrantless evidentiary search of a home over a present resident's objection.
The rule does not prevent police from entering when an independent justification exists. Officers may enter to address an objectively supported threat of domestic violence or another emergency, and may seize evidence in plain view while lawfully present. But those protective or exigent-circumstances doctrines are distinct from consent to conduct an evidentiary search.