Understanding Search and Seizure Law: Fourth Amendment Essentials

The Fourth Amendment in a Nutshell

The Fourth Amendment to the United States Constitution protects people from unreasonable searches and seizures by the government. It provides that warrants must be supported by probable cause, sworn under oath or affirmation, and must particularly describe the place to be searched and the persons or things to be seized. Criminal law paralegals frequently help prepare motions to suppress evidence, and certification exams regularly test the core rules. This guide explains them in clear terms.

When Does the Fourth Amendment Apply?

What Is a Search?

A search occurs when the government intrudes on a person's reasonable expectation of privacy, a test derived from Katz v. United States, or when it physically intrudes on a constitutionally protected area such as the home, as the Court held in United States v. Jones. A person must have a subjective expectation of privacy that society recognizes as reasonable. Examples that are generally not searches include looking at what is in plain view from a public place, examining items abandoned in a public trash bin, and flying over a yard in public airspace at a reasonable altitude. By contrast, using thermal imaging on a home or accessing historical cell site location information over a long period generally requires a warrant.

What Is a Seizure?

A seizure of property occurs when there is meaningful interference with a person's possessory interests. A seizure of a person occurs when, in view of all the circumstances, a reasonable person would not feel free to leave or otherwise end the encounter. Mere questioning in a public place is not a seizure, but physically restraining someone or displaying authority in a way that restricts movement can be.

Who Is Bound by the Fourth Amendment?

The Amendment restrains government actors. Searches by private individuals who are not acting as government agents do not trigger it. The Amendment applies to the states through the Fourteenth Amendment. A person can only challenge a search if their own rights were violated, which is known as having standing, and a passenger in a car, for example, generally cannot challenge a search of the vehicle itself, although the passenger may challenge the stop.

The Warrant Requirement and Probable Cause

As a general rule, searches conducted without a warrant are presumptively unreasonable. To obtain a warrant, officers must present an affidavit to a neutral and detached magistrate showing probable cause, meaning a fair probability that contraband or evidence of a crime will be found in the place to be searched. Courts apply the totality of the circumstances test from Illinois v. Gates. The warrant must describe the place and items with particularity. If officers exceed the scope of the warrant, the excess search may be unlawful.

Exceptions to the Warrant Requirement

Courts recognize several exceptions. Remember them with this list.

Search Incident to Lawful Arrest

Officers may search a person arrested and the area within the arrestee's immediate control. For vehicles, Arizona v. Gant limits this to situations where the arrestee is unsecured and within reaching distance of the passenger compartment, or where it is reasonable to believe evidence of the offense of arrest is in the vehicle. Cell phones generally require a warrant even after arrest, according to Riley v. California.

Consent

A search is valid if a person with actual or apparent authority voluntarily consents. Consent need not be accompanied by a warning that the person can refuse, though that fact is relevant. Consent can be limited or withdrawn. If two occupants with equal authority are present and one objects, the objecting occupant's refusal controls.

Plain View

Officers may seize an object without a warrant if they are lawfully present, the object is in plain view, and its incriminating nature is immediately apparent. Officers cannot move items to see their serial numbers or markings without separate justification.

Automobile Exception

If officers have probable cause to believe a vehicle contains contraband or evidence of crime, they may search the entire vehicle and containers inside that could hold the item sought, without a warrant. This exception rests on the mobility of vehicles and reduced expectations of privacy.

Exigent Circumstances

Emergency situations such as hot pursuit of a fleeing suspect, imminent destruction of evidence, or the need to prevent harm can justify immediate warrantless entry.

Stop and Frisk

Under Terry v. Ohio, an officer who has reasonable suspicion that criminal activity is afoot may briefly detain a person. If the officer reasonably believes the person is armed and dangerous, the officer may pat down the outer clothing for weapons. Reasonable suspicion requires specific and articulable facts, which is less than probable cause but more than a hunch.

Other Exceptions

• Inventory searches of impounded vehicles under standardized procedures
• Border searches, which require no warrant or suspicion for routine searches
• Special needs and administrative searches, such as sobriety checkpoints
• Protective sweeps incident to an in-home arrest

The Exclusionary Rule

What Is the Exclusionary Rule?

Evidence obtained in violation of the Fourth Amendment is generally inadmissible against the defendant at trial. Mapp v. Ohio applied this rule to state courts. The rule also reaches derivative evidence, known as fruit of the poisonous tree, which is evidence discovered because of the initial illegality.

What Are the Exceptions to Exclusion?

• Independent source: the evidence was also obtained through a lawful, separate route.
• Inevitable discovery: the evidence would have been found anyway by lawful means.
• Attenuation: the link between the illegality and the evidence is so weak that the taint is purged.
• Good faith: officers reasonably relied on a warrant later found defective, as in United States v. Leon.

Illegally obtained evidence may still be used in some proceedings, such as grand jury hearings, and to impeach a defendant who testifies inconsistently.

How Paralegals Help With Suppression Issues

When a defense attorney challenges a search, a paralegal gathers police reports, body camera footage, warrant affidavits, and dispatch logs. You may prepare a timeline of events, summarize case law, and draft portions of a motion to suppress. Pay close attention to details such as who consented, what the officer said, and when each event happened. On the prosecution side, paralegals help ensure warrants are accurately described and that evidence chain of custody is documented.

Exam Tips

When you see a search and seizure question, work through a consistent method. First, was there a search or seizure by the government? Second, did the person have standing? Third, was there a warrant? Fourth, if not, does an exception apply? Fifth, if the search was unlawful, does the exclusionary rule apply or does an exception to exclusion save the evidence? Practice this checklist with our criminal law flashcards. You can start for free to test yourself, and the pricing page shows how to unlock complete practice exams.

Key Takeaways

The Fourth Amendment requires a warrant based on probable cause unless an exception applies. The most tested exceptions are search incident to arrest, consent, plain view, automobile, exigent circumstances, and stop and frisk. Unlawfully obtained evidence is usually excluded, subject to the independent source, inevitable discovery, attenuation, and good faith doctrines.