The term probable cause is found within the second clause of the Fourth Amendment. In the wording of this clause probable cause refers to the amount of justification required for issuing a warrant: “No warrant shall issue but upon probable cause.” Despite this specific wording indicating the applicability of probable cause only for warrants, probable cause also became the standard for justifying warrantless criminal searches and arrests. If a warrant is issued, a magistrate makes the determination of probable cause. If no warrant has been issued, an officer in the field generally makes the determination. The Court has held that the standard of justification for searches without a warrant cannot be less than if a warrant were required. In Henry v. United States (1959), the Court explained that “If the officer acts with probable cause, he is protected even though it turns out that the citizen is innocent…and while a search without a warrant is…permissible if incident to a lawful arrest, if an arrest without a warrant is to support an incidental search, it must be made with probable cause.” In addition, a lesser standard would encourage warrantless activity.
The standard for probable cause is met when the facts and circumstances known to the police officer consist of sufficiently trustworthy information to warrant a reasonably prudent person in believing, in the case of a search, that an item related to criminal activity would be found in a certain place, or in the case of arrest, that the arrested person had committed, or was committing, a crime (Beck v. State of Ohio, 1964). This standard addresses both the amount of information the officer possesses, as well as the reliability of that information. In a search for items related to a crime that will be found at a particular place, the information