When someone invites the police into his or her home, the police need neither PROBABLE CAUSE nor a warrant to accept the invitation. Acting on one person's invitation or consent to search, however, the police may uncover evidence that incriminates some other person. For example, a spouse or child may consent to a search that uncovers evidence against another spouse or a parent; a landlord may permit a search that reveals evidence useful in prosecuting the landlord's tenant; a common carrier may authorize the police to open a package shipped by a suspected drug dealer; or a school principal may authorize the police to search a student's locker. In litigation under the FOURTH AMENDMENT, the issues raised by cases of this sort have been treated under the rubric "third-party consent." Courts have held that the consent of someone other than the person against whom evidence is offered can sometimes justify seizure of this evidence despite the lack of probable cause or a SEARCH WARRANT.
No unitary theory explains when third-party consent justifies a search under the Fourth Amendment. In some cases, courts have invoked concepts of agency. In an extreme and unlikely case, the agency might be express; a person might execute a document authorizing an agent to admit the police to his or her premises at the agent's unfettered discretion. In these circumstances, a court could easily conclude that the principal himself or herself had authorized the search. Agency principles appear to justify both holdings that a manager of business premises may consent to a search that uncovers evidence against the owner of the business and rulings that the consent of a secretary or maintenance worker to a search of areas not open to casual visitors is ordinarily insufficient.
Courts also have upheld third-party consent searches that could not have been justified on agency principles. For example, a husband may assault his wife, and the wife may admit the police to the home that she owns with her husband to reveal the location of the assault weapon. In this case, the husband may be present and may inform the police that his wife has no authority to waive his Fourth Amendment rights. When the wife admits the police, however, she does not act as the agent of her husband, and
she does not waive his rights. Instead, she exercises her own PROPERTY RIGHTS. As in other cases of third-party consent, the husband's Fourth Amendment rights...