The Constitutional prohibition against unreasonable searches and seizures by the government is one of the most important principles of criminal law.
The Fourth Amendment to the United States Constitution states:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
— US Const., amend. 4 (1791)
The Fourth Amendment creates a constitutional buffer between U.S. citizens and the intimidating power of law enforcement. It has three components. First, it establishes a privacy interest by recognizing the right of U.S. citizens to be “secure in their persons, houses, papers, and effects.” Second, it protects this privacy interest by prohibiting searches and seizures that are “unreasonable” or that are not authorized by a warrant based upon probable cause. Third, it requires that the warrant describes with particularity “the place to be searched, and the persons or things to be seized.”