Fourth Amendment Basics

The Fourth Amendment protects against unreasonable searches and seizures by government actors.

Related Fourth Amendment rules

• Reasonable Expectation of PrivacyA search occurs when government intrudes on a reasonable expectation of privacy.
• Standing to Challenge SearchStanding requires the defendant to have a personal privacy interest in the place or item searched.
• Warrant RequirementsWarrants require probable cause, oath, and particularity describing place and items to be searched.
• Probable Cause StandardProbable cause exists when facts would lead a reasonable person to believe evidence or contraband will be found.
• Particularity RequirementWarrants must specifically describe the place to be searched and items to be seized.
• Knock-and-Announce RulePolice must knock and announce unless reasonable suspicion of danger, futility, or evidence destruction exists.
• Search Incident to ArrestSearch incident to a lawful arrest permits searching arrestee and immediate control area.
• Automobile SearchesPolice may search a vehicle with probable cause that it contains contraband or evidence.

Part of Criminal Procedure on Core Legal Rules — foundational MBE-tested principles with primary-source citations.