Fourth Amendment (1791)

Individuals are protected “in their persons, houses, papers and effects” from unreasonable searches. If the police—agents of the executive branch—wish to search a home or other place for evidence of a crime, they must first convince a judge—the judicial branch—that there is enough evidence to obtain a search warrant. The court must decide if “probable cause” exists to issue a warrant, and the warrant must list the place to be searched and the evidence police believe they will find.

The Fourth Amendment’s warrant requirement is an example of the Constitution‘s system of checks and balances, and is key to ensuring liberty and justice.

The Founders believed that freedom from government intrusion into one’s home was a natural right and fundamental to liberty. During the colonial era, lawyer James Otis argued in court against British use of writs of assistance, which were general search warrants allowing British officials to search wherever they wanted without having to say why. His arguments were observed by John Adams, who noted that Otis’s argument against this form of British tyranny marked the beginning of the American Revolution. George Mason wrote in the Virginia Declaration of Rights that general search warrants were “grievous and oppressive and ought not to be granted.”

The Court has held that some searches are reasonable even without a warrant. Some exceptions to the warrant requirements include searches of individuals who have consented to a search and people who have been lawfully arrested. Additionally, police can legally frisk people behaving suspiciously. A warrant is not needed for discovery of evidence while police are “in hot pursuit” of a suspect, or if an officer sees incriminating evidence in plain sight somewhere the officer is legally allowed to be.

Landmark Supreme Court cases involving the Fourth Amendment include Mapp v. Ohio (1961), New Jersey v. T.L.O. (1985), and Board of Education of Pottawatomie County v. Earls (2002).