← The hardest concepts in United States law
In one breath
A search is presumed unreasonable unless a judge approved it in advance by warrant, resting on probable cause. A short list of recognized exceptions, such as consent, exigency, searches of vehicles and searches incident to arrest, lets officers search without one, each with its own conditions and limits.
The picture
The locked house with marked side doors
Picture a house whose front door is locked and needs the key of an outside keeper: the warrant. Anyone who comes in by the front door is expected to have the keeper’s approval, and the keeper gave it only after being shown good reason. There are also a few side doors, each with a sign on it. One says “Fire: enter if someone inside is in danger.” One says “Open to those invited in.” One says “Vehicles only: bring your own reason.” No sign, no entry.
Each sign tells you more than who may use the door. It tells you what the visitor may do inside. A door for rescuing a person lets you look for the person, not open the desk drawers. The door for an arrest lets you search the arrested person and the space within their reach, not the whole house. The scope of each exception is set by the reason that justified opening it.
Where the picture stops working
The side doors are not a literal list on a wall. They are results of judicial decisions about reasonableness, and the courts have refined their limits over time. The picture also starts too late: some government actions are not searches at all, because they intrude on no protected privacy, and then the house is never reached.
How it really works
- 1Ask whether a search or seizure occurred at all: did the government intrude on a place or thing in which a person has a reasonable expectation of privacy (Katz), or physically enter a protected area such as the home?
- 2Ask whether there was a warrant, issued by a neutral magistrate on probable cause and describing the place and the things to be seized.
- 3If not, identify the exception and check each of its conditions. Consent must be voluntary, judged from the totality of the circumstances (Schneckloth). The vehicle exception requires probable cause to believe the vehicle holds evidence or contraband (Carroll).
- 4Check scope. A search incident to a lawful arrest is limited to the arrestee’s person and the area within their reach (Chimel). Exigent circumstances, such as hot pursuit of a suspect or an immediate danger to life, justify a search only to the extent the emergency requires. Plain view needs a lawful position and an immediately apparent incriminating character.
- 5If the search was unlawful, ask about the remedy. Evidence is usually excluded from the prosecution’s case (Mapp v. Ohio), subject to its own exceptions, such as independent source and good faith.
Why people get it wrong
- Thinking the exceptions are loopholes with no limits. Each has conditions and a scope that follows from its purpose.
- Treating probable cause and a warrant as one thing. Many exceptions still require probable cause; they just remove the need to go to a judge first.
- Confusing a stop with a search or an arrest. Brief stops and frisks need reasonable suspicion (Terry v. Ohio), which is less than probable cause and permits less.
- Forgetting consent can be limited or withdrawn, and that officers may rely on apparent authority of the person who consents.
- Assuming a violation always frees the defendant. Exclusion is a remedy for evidence, with exceptions, and not a bar to prosecution.
A worked example
The facts are invented
Officers in the invented city of Calder arrest Dev on a warrant outside his apartment. They search his pockets and the bag he is carrying, which is lawful as a search incident to arrest. They then walk into the apartment without a warrant to search it. Without more, that goes beyond the area within his reach and is not justified by the arrest.
Change the facts: as they arrest him they hear a cry for help from inside. Exigent circumstances now allow them in to look for the person in danger, but not to open the cabinets in the kitchen. If, while they are lawfully in the room, they see jewelry that is plainly the subject of a theft report lying on the table, plain view may allow its seizure. If instead Dev’s flatmate says “come in” and has authority over the shared room, consent may justify the entry, and again the search is limited to the shared space.
Try it
Officers lawfully arrest a driver and handcuff him in their car. Without a warrant, they search his house, saying it is a search incident to arrest. Is the search justified on that ground?
Landmark authorities
Read the sources themselves; this list is a starting point.
- Carroll v. United States, 267 U.S. 132 (1925)
- Mapp v. Ohio, 367 U.S. 643 (1961)
- Katz v. United States, 389 U.S. 347 (1967)
- Terry v. Ohio, 392 U.S. 1 (1968)
- Chimel v. California, 395 U.S. 752 (1969)
- Schneckloth v. Bustamonte, 412 U.S. 218 (1973)
Where to go next
Dictionary
More hard concepts in United States law
- Miranda: custody plus interrogation (Criminal procedure)
- The Eleventh Amendment and state sovereign immunity (Constitutional law)
This page is an educational overview. It is not legal advice and not a substitute for the sources: the statute, the rule, the case itself. United States law is made in fifty states and in the federal system, and the rules differ between them. Each page states the usual formulation of the rule and names landmark decisions; your own state, circuit or course may use different wording. Check the primary sources before relying on any rule.