A warrant is the ordinary model for a substantial search. A neutral magistrate must find probable cause, supported by oath or affirmation, and the warrant must particularly describe the place to be searched and the persons or things to be seized. Probable cause is a practical, common-sense probability, not proof beyond a reasonable doubt. Particularity prevents a general rummaging search. Yet the amendment forbids unreasonable searches, not every warrantless search. Consent, a search incident to a lawful arrest, exigent circumstances, the automobile doctrine, and narrowly defined special-needs rules are among the recognized exceptions.

Different intrusions use different thresholds. Under Terry v. Ohio, specific and articulable facts creating reasonable suspicion may justify a brief stop. A protective frisk additionally requires reasonable suspicion that the person is armed and dangerous; it is a limited search for weapons, not a general evidence search. Digital technology complicates older categories because a phone or a long record of location data can reveal far more than a physical object. The governing question remains what information or property government obtained and whether its method was reasonable.

In a scenario, proceed in sequence: identify government action; decide whether there was a search or seizure; determine the required justification; test any warrant or exception; then consider the remedy. If an officer opens a home's locked drawer without consent, a warrant, or emergency, the core protection is implicated. If the homeowner voluntarily permits the exact search conducted, consent may make it reasonable. The constitutional violation and exclusion of evidence are separate questions; an unlawful search does not automatically establish that every resulting item must be suppressed.

Video lesson: Search and Seizure: Crash Course Government and Politics #27