Probable Cause

Legal term referring to the minimum standard of evidence needed for a magistrate to issue a search warrant. There are various legal definitions for the term, but probable cause requires “belief that the law was being violated on the premises to be searched; and … the facts … are such that a reasonably discreet and prudent man would be led to believe that there was a commission of the offense charged.”

In Nathanson v. United States (1933), the Court ruled that a sworn statement not adequately supported by facts, does not constitute probable cause to issue a warrant:

The Court has held valid warrants based on hearsay, and it has not required direct personal observation of the facts or circumstances justifying the warrant by the individual who seeks it. The magistrate, however, must be satisfied that the informant is credible or the information reliable.

Only if an individual cannot or does not consent to a search are police required to obtain a warrant. Voluntary consent of the individual who owns or occupies the place to be searched validates the search. The Court, however, has held that the individual who is asked to consent to a search need not be informed that he or she may refuse. In Schneckloth v. Bustamonte (1973), the Court discussed the elements of voluntary consent:

The following year, in United States v. Matlock (1974), the Court held that when one occupant of a house consents to a search of the premises, the search is proper, and evidence uncovered in it may be used against another occupant. In 1990, in another case involving multiple occupants of a residence, the Court ruled that an overnight houseguest has a legitimate expectation of privacy and is entitled to Fourth Amendment protection against police intrusion at the house. By a vote of 7-2, the justices said the guest has sufficient interest in the home to challenge the legality of his warrantless arrest there.