3. 4th Amendment

Fourth Amendment (1791)

Protects individuals against unreasonable searches and seizures by the government and establishes requirements for search warrants based on probable cause.

Fourth Amendment (Text Summary)

Protects the people against unreasonable searches and seizures and requires warrants to be supported by probable cause, supported by oath or affirmation, and particularly describing the place to be searched and the persons or things to be seized.

Fourth Amendment (Purpose)

Protect individual privacy, property, and liberty by limiting arbitrary government intrusion.

Search

A government intrusion into an area where an individual has a reasonable expectation of privacy to obtain information or evidence.

Seizure

A meaningful interference by the government with an individual's person, property, or freedom of movement.

Unreasonable Search and Seizure

A search or seizure conducted without constitutional justification, usually without a valid warrant or recognized exception.

Reasonable Search

A government search that complies with the Fourth Amendment because it is supported by a warrant or a recognized exception.

Reasonable Expectation of Privacy

The constitutional standard determining whether government conduct constitutes a search under the Fourth Amendment.

Katz Test

The constitutional test asking whether an individual had a subjective expectation of privacy that society recognizes as reasonable.

Reasonable Expectation of Privacy Doctrine

The principle established in Katz v. United States that the Fourth Amendment protects people rather than places.

Privacy Interest

An individual's constitutionally protected interest in remaining free from unreasonable government intrusion.

Government Intrusion

Official interference with an individual's privacy, property, or personal security.

Search Warrant

A written court order authorizing law enforcement to conduct a search of a specified location or seize specified items.

Warrant Requirement

The constitutional principle that searches generally require judicial authorization unless an established exception applies.

Valid Warrant

A warrant issued by a neutral magistrate based on probable cause and describing with particularity the place to be searched and items to be seized.

Neutral and Detached Magistrate

An impartial judicial officer responsible for determining whether probable cause exists before issuing a warrant.

Probable Cause

Reasonable grounds for believing that a crime has been committed or that evidence of a crime will be found in the place to be searched.

Probable Cause Standard

The constitutional level of evidence generally required before issuing a search warrant or making many arrests.

Oath or Affirmation Requirement

The Fourth Amendment requirement that warrant applications be supported by sworn statements.

Particularity Requirement

The constitutional requirement that warrants specifically identify the place to be searched and the persons or items to be seized.

General Warrant

A broad warrant allowing unrestricted searches; prohibited by the Fourth Amendment.

Writ of Assistance

A general search authorization used by British officials before the American Revolution and one of the historical reasons for adopting the Fourth Amendment.

Colonial Opposition to Writs of Assistance

American colonists objected to unlimited British search authority, helping inspire Fourth Amendment protections.

Arrest Warrant

A judicial order authorizing law enforcement to arrest a specific individual.

Search Incident to Arrest

A recognized exception allowing officers to search an arrestee and the area within immediate control following a lawful arrest.

Exigent Circumstances

Emergency situations permitting warrantless searches when waiting for a warrant would threaten safety, allow escape, or risk destruction of evidence.

Hot Pursuit

Exception allowing officers to enter property without a warrant while immediately pursuing a fleeing suspect.

Consent Search

A warrantless search conducted after an individual voluntarily gives permission.

Voluntary Consent

Permission given freely without coercion, making a consent search constitutional.

Plain View Doctrine

The rule allowing officers lawfully present to seize evidence that is immediately recognizable as contraband or evidence of a crime.

Automobile Exception

The rule allowing warrantless vehicle searches based on probable cause because vehicles are mobile.

Vehicle Search Doctrine

The constitutional rules governing warrantless searches of automobiles.

Stop and Frisk

A brief detention and limited pat-down search for weapons based on reasonable suspicion.

Terry Stop

Another name for a stop and frisk conducted under Terry v. Ohio.

Reasonable Suspicion

A lower standard than probable cause requiring specific, articulable facts suggesting criminal activity.

Investigatory Stop

A temporary detention based on reasonable suspicion rather than probable cause.

Protective Pat-Down

A limited frisk conducted to determine whether a suspect possesses weapons.

Administrative Search

A search conducted for regulatory or public safety purposes rather than criminal investigation.

Border Search Exception

The rule allowing routine searches at international borders without warrants or probable cause.

School Search Doctrine

The constitutional rules permitting school officials to conduct reasonable searches of students under a lower standard than police.

Special Needs Doctrine

The principle allowing certain warrantless searches serving governmental interests beyond ordinary law enforcement.

Inventory Search

A search of lawfully impounded property conducted to document its contents rather than investigate crime.

Community Caretaking Doctrine

The principle recognizing some non-investigatory police activities serving public safety.

Electronic Surveillance

Government monitoring of communications or electronic information subject to Fourth Amendment protections.

Digital Privacy

Constitutional protections involving electronic devices, digital information, and modern technology.

Cell Phone Search

A search of digital information stored on a mobile phone, generally requiring a warrant.

GPS Tracking

Government monitoring of a person's location using electronic tracking devices.

Thermal Imaging Search

Government use of heat-sensing technology to detect activity inside a home.

Exclusionary Rule

The constitutional rule preventing illegally obtained evidence from being used in criminal prosecutions.

Exclusionary Rule (Purpose)

Deter police misconduct by excluding evidence obtained in violation of the Fourth Amendment.

Fruit of the Poisonous Tree Doctrine

Evidence derived from an unconstitutional search or seizure is generally inadmissible in court.

Derivative Evidence

Evidence discovered because of previously obtained illegal evidence.

Independent Source Doctrine

Exception allowing admission of evidence later obtained from an independent lawful source.

Inevitable Discovery Doctrine

Exception permitting evidence that would inevitably have been discovered through lawful means.

Attenuation Doctrine

Exception allowing evidence when the connection between unconstitutional police conduct and the evidence has become sufficiently weakened.

Good Faith Exception

The rule allowing evidence obtained by officers reasonably relying on a defective warrant.

Standing (Fourth Amendment)

The legal requirement that only individuals whose own Fourth Amendment rights were violated may challenge a search.

Open Fields Doctrine

The rule that open fields generally receive no Fourth Amendment protection.

Curtilage

The area immediately surrounding a home that generally receives Fourth Amendment protection.

Home Doctrine

The constitutional principle recognizing the home as receiving the highest level of Fourth Amendment protection.

Knock-and-Announce Rule

The traditional requirement that officers generally announce their presence before executing a search warrant.

No-Knock Warrant

A warrant authorizing officers to enter without prior announcement under limited circumstances.

Wiretap

Government interception of telephone or electronic communications.

Electronic Eavesdropping

Government monitoring of private communications through electronic means.

Katz v. United States (1967)

Supreme Court case establishing that the Fourth Amendment protects people rather than places.

Katz v. United States (1967) (Facts)

Federal agents secretly recorded conversations from a public telephone booth without a warrant.

Katz v. United States (1967) (Holding)

The government's electronic surveillance violated Katz's reasonable expectation of privacy.

Katz v. United States (1967) (Significance)

Created the Reasonable Expectation of Privacy Test.

Mapp v. Ohio (1961)

Supreme Court case applying the Exclusionary Rule to state governments through the Fourteenth Amendment.

Mapp v. Ohio (1961) (Facts)

Police conducted an unlawful search of Dollree Mapp's home and discovered evidence used against her.

Mapp v. Ohio (1961) (Holding)

Evidence obtained through unconstitutional searches cannot be used in state criminal prosecutions.

Mapp v. Ohio (1961) (Significance)

Incorporated the Exclusionary Rule against the states.

Weeks v. United States (1914)

Supreme Court case establishing the Exclusionary Rule for federal prosecutions.

Weeks v. United States (1914) (Significance)

Created the federal Exclusionary Rule later incorporated through Mapp.

Terry v. Ohio (1968)

Supreme Court case allowing stop and frisk based on reasonable suspicion.

Terry v. Ohio (1968) (Facts)

A police officer stopped and frisked three men suspected of preparing to commit a robbery.

Terry v. Ohio (1968) (Holding)

Brief investigative stops and protective frisks are constitutional with reasonable suspicion.

Terry v. Ohio (1968) (Significance)

Established the Reasonable Suspicion Standard.

United States v. Leon (1984)

Supreme Court case creating the Good Faith Exception to the Exclusionary Rule.

United States v. Leon (1984) (Holding)

Evidence obtained through reasonable reliance on a defective warrant may still be admitted.

Illinois v. Gates (1983)

Supreme Court case adopting the Totality of the Circumstances Test for determining probable cause.

Illinois v. Gates (1983) (Holding)

Judges should evaluate probable cause based on all relevant circumstances rather than rigid factors.

Totality of the Circumstances Test

The flexible approach used to determine whether probable cause exists.

Riley v. California (2014)

Supreme Court case holding that police generally must obtain a warrant before searching the digital contents of a cell phone seized during an arrest.

Riley v. California (2014) (Significance)

Expanded Fourth Amendment protections for digital privacy.

Carpenter v. United States (2018)

Supreme Court case holding that police generally need a warrant to obtain historical cell-site location information.

Carpenter v. United States (2018) (Significance)

Recognized strong Fourth Amendment protections for digital location data.

Kyllo v. United States (2001)

Supreme Court case holding that warrantless thermal imaging of a home violates the Fourth Amendment.

United States v. Jones (2012)

Supreme Court case holding that attaching a GPS tracking device to a vehicle constitutes a search under the Fourth Amendment.

Fourth Amendment Incorporation

The application of Fourth Amendment protections against state governments through the Fourteenth Amendment's Due Process Clause.

Privacy Doctrine

The constitutional principle recognizing privacy interests against unreasonable government intrusion.

Search and Seizure Jurisprudence

The body of constitutional law governing government searches, seizures, warrants, privacy, and law enforcement practices.