Fourth Amendment Law: Probable Cause, Warrants, Searches & Exclusion

Posted on Mar 2, 2026 in Law

Probable Cause Hearings

Gerstein v. Pugh: The Fourth Amendment requires a prompt judicial determination of probable cause as a prerequisite to extended pretrial detention following a warrantless arrest.

County of Riverside v. McLaughlin: A jurisdiction that provides judicial determinations of probable cause within 48 hours of a warrantless arrest generally complies with the Fourth Amendment. Delays beyond 48 hours are presumptively unreasonable unless justified by extraordinary circumstances.

Pre-Arrest Investigation: Police gather evidence through interviews, forensic tests, and surveillance.
Arrest and Detention: Detentions can occur before formal arrests (traffic stops).
Post-Arrest Investigation: Further evidence gathering, additional victim testimonies.
Decision to Charge: Officers decide initial charges; prosecutors may revise.
Preliminary Hearings: Determine probable cause within 14 days of arrest. Can result in charge reduction, dismissal, or case settlement.
Grand Jury: Twelve jurors decide on probable cause; a safeguard against wrongful charges.
Arraignment: Formal presentation of charges. Defendant enters a plea.
Pre-Trial Motions: Defense may file motions to suppress evidence or challenge procedures.
Trial and Sentencing: Jury determines guilt or innocence. Sentencing follows if guilty.
Appeals and Post-Conviction Relief: Appeals to higher courts on procedural or substantive grounds. Post-conviction petitions address ineffective counsel or new evidence.

Pretrial Release

Stack v. Boyle: Bail set at an amount higher than necessary to ensure the defendant’s appearance at trial is “excessive” under the Eighth Amendment.

U.S. v. Salerno: Preventive detention can be constitutional when the government demonstrates that no conditions of release can reasonably assure the safety of the community.

State v. Burgins (Tenn.): Tennessee law permits a court to impose pretrial conditions (including no-bond detention) if the court finds clear and convincing evidence that the defendant poses a danger to the community and no less restrictive conditions will ensure public safety.

Relevant Constitutional Provisions

Fifth Amendment: Protects against self-incrimination and double jeopardy; guarantees due process before depriving life, liberty, or property.
Eighth Amendment: Prohibits excessive bail, excessive fines, and cruel and unusual punishment.
Fourteenth Amendment: Incorporates key Bill of Rights protections to state actions through selective incorporation; requires due process and equal protection under the law.
Fourth Amendment: The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.

The Nature and Scope of Due Process

Duncan v. Louisiana: States must provide jury trials in serious criminal cases.

District Attorney’s Office v. Osborne: There is no substantive due process right under the U.S. Constitution for a convicted individual to obtain post-conviction access to the state’s DNA evidence for testing. The Court deferred to state procedures for such requests.

Probable Cause Hearing: Establishes if there is probable cause for an offense and connection to the accused.

Determines bail eligibility and conditions.

The Exclusionary Rule

Mapp v. Ohio: Evidence obtained in violation of the Fourth Amendment is inadmissible.

Hudson v. Michigan: A violation of the knock-and-announce rule does not require suppression of evidence found during a search.

Herring v. U.S.: The exclusionary rule does not apply to evidence obtained through isolated negligence by police rather than systematic error or reckless disregard of constitutional rights.

State v. McElrath (Tenn.): Tennessee adopted the good-faith exception to the exclusionary rule.

State v. McLawhorn (Tenn.): Under Tennessee law, the exclusionary rule does not apply where an officer acts in objectively reasonable reliance on a warrant that is later found to be invalid, aligning with the good-faith exception recognized in U.S. v. Leon. Evidence obtained under such circumstances is admissible.

Exclusionary Rule Concepts

Exclusionary Rule: Evidence obtained in violation of the Fourth Amendment cannot be used in court to prove guilt.

Good-Faith Exception: Evidence is admissible if law enforcement:

Relied on a warrant they believed was valid.
Acted on laws or rules later declared unconstitutional.
Operated under faulty information not due to their own negligence.

Knock-and-Announce Rule: Officers must generally knock and announce their presence before entering unless:

There is a risk of evidence destruction.
The safety of officers is at stake.

Protected Areas and Interests

Katz v. United States: The Fourth Amendment protects people, not places. A search occurs when the government violates a person’s reasonable expectation of privacy, even without physical intrusion.

California v. Greenwood: The Fourth Amendment does not prohibit warrantless searches and seizures of trash left outside the home for collection, because individuals have no reasonable expectation of privacy in garbage exposed to the public.

Florida v. Riley: Aerial surveillance of a partially enclosed structure (e.g., a greenhouse) from public airspace (400 feet) does not constitute a Fourth Amendment search if it does not interfere with normal use and the observation is made from a lawful vantage point.

U.S. v. Jones: Physically placing a GPS tracking device on a vehicle and using it to monitor movements constitutes a search under the Fourth Amendment.

Carpenter v. U.S.: The government must obtain a search warrant supported by probable cause to access a person’s historical cell-site location information (CSLI). Individuals maintain a reasonable expectation of privacy in their physical movements recorded by cell phone data.

Florida v. Jardines: Bringing a drug-sniffing dog onto the curtilage of a home to investigate for narcotics is a Fourth Amendment search and requires a warrant. This ruling emphasized property-based protections, not just privacy expectations.

U.S. v. White: A defendant has no reasonable expectation of privacy in conversations voluntarily shared with an informant, even if the informant is wearing a wire. The Fourth Amendment is not violated when such conversations are recorded or transmitted.

Torres v. Madrid: A seizure occurs under the Fourth Amendment when an officer applies physical force with intent to restrain, even if the person does not submit and gets away. This clarified that physical contact alone, intended as a restraint, triggers constitutional protection.

Zurcher v. Stanford Daily: The Fourth Amendment allows police to search third-party premises (such as a newsroom) with a valid warrant if they believe evidence of a crime is there. There is no special immunity for the press from generally applicable search warrants.

Doctrines and Principles

Justified Expectation of Privacy: Depends on social norms and the individual’s conduct.
Open Fields Doctrine: No expectation of privacy in open fields.
Third-Party Doctrine: Allows law enforcement to obtain information shared with third parties without a warrant. The doctrine states that people who voluntarily share information with third parties lose their expectation of privacy in that information (e.g., bank statements, telephone records).

Probable Cause

Illinois v. Gates: Replaced Aguilar-Spinelli with the “totality-of-the-circumstances” test to determine probable cause for a warrant. Courts should assess whether there is a fair probability that contraband or evidence will be found in a particular place.

State v. Tuttle (Tenn.): Under Article I, Section 7 of the Tennessee Constitution, courts should apply the totality-of-the-circumstances test to determine whether a search warrant affidavit establishes probable cause. This decision overruled the prior precedent set in State v. Jacumin, 778 S.W.2d 430 (Tenn. 1989), which had mandated the stricter Aguilar-Spinelli two-pronged test.

Probable Cause: There is a reasonable basis for believing that a crime may have been committed.

Reasonable Suspicion: Specific and articulable facts drawn from observed behaviors or circumstances that justify a seizure.

Search Warrants

Maryland v. Pringle: When drugs or contraband are found in a vehicle, and ownership is unclear, officers may have probable cause to arrest all occupants if a reasonable officer could conclude joint possession.

Maryland v. Garrison: A search executed under a valid warrant does not violate the Fourth Amendment if officers reasonably but mistakenly believe they are searching the correct area. Good-faith mistakes in executing a search do not invalidate the warrant’s use.

Richards v. Wisconsin: There is no blanket exception to the knock-and-announce requirement for drug cases. However, officers may dispense with knocking and announcing if they have reasonable suspicion that announcing would be dangerous, futile, or inhibit the investigation (e.g., destruction of evidence).

Franks v. Delaware: A defendant is entitled to a hearing to challenge the validity of a search warrant if they make a substantial preliminary showing that:

the affidavit supporting the warrant contained a false statement,
the falsehood was made knowingly, intentionally, or with reckless disregard for the truth, and
the allegedly false statement was necessary to the finding of probable cause.

If these conditions are met and the false material is removed, and the remaining content does not establish probable cause, the warrant is invalid and the evidence must be suppressed.

State v. Little (Tenn.): Under Tennessee law, a search warrant affidavit must state facts and circumstances establishing probable cause. A bare conclusion or statement of belief is insufficient. The magistrate must be able to independently determine the existence of probable cause from the affidavit itself.

Types of Warrants and Concepts

Traditional Warrant: Issued based on probable cause.
Anticipatory Warrant: Valid if there is probable cause to believe that evidence will be present when the warrant is executed. Requirements:
1. Probable cause that contraband or evidence will be at the location when the conditions of the warrant are fulfilled.
2. The conditions triggering the warrant are likely to occur.
Totality of the Circumstances: Determines voluntariness and includes factors such as suspect’s age, education, duration of interrogation, coercion, deception, and mental state.
Custody: Whether, under the totality of the circumstances, a reasonable person would consider himself or herself deprived of freedom of movement to a degree associated with a formal arrest.
Public Safety Exception: Applies when there is an urgent threat (hidden gun, bomb); no Miranda warnings are required.

Arrest and Search of Persons

U.S. v. Watson: The Fourth Amendment permits warrantless arrests in public if law enforcement officers have probable cause to believe the suspect has committed a felony. There is no constitutional requirement for a warrant before such arrests.

U.S. v. Robinson: A full search of a person incident to a lawful custodial arrest is always reasonable under the Fourth Amendment, even if there is no specific concern for officer safety or preservation of evidence.

Whren v. U.S.: A traffic stop is constitutional if officers have probable cause to believe a traffic violation occurred, regardless of their subjective motivations for making the stop.

Atwater v. City of Lago Vista: The Fourth Amendment permits a warrantless arrest for a misdemeanor committed in the officer’s presence, even if the offense is punishable only by a fine.

Maryland v. King: Collecting a DNA sample via cheek swab from an individual lawfully arrested for a serious offense is a reasonable search under the Fourth Amendment for purposes of identification.

Public Arrests: Arrests in public for felonies or misdemeanors observed by the officer do not require a warrant.

Exceptions to the Warrant Requirement

1. Search incident to lawful arrest: Officers may search the person and the area within their immediate control (the “grab area”).

Purpose: Officer safety and prevention of evidence destruction.
Officers may not search beyond the immediate control area without a warrant.
A full search is permissible incident to a lawful custodial arrest, regardless of the specific evidence sought.
Police scraped evidence (blood) from under a suspect’s fingernails without a formal arrest. The search was permissible because it occurred along with probable cause.

Seizure and Search of Premises

Mitchell v. Wisconsin: When a DUI suspect is unconscious, and therefore cannot submit to a breath test, the police may generally conduct a warrantless blood draw under the exigent circumstances exception, provided there is probable cause to believe the suspect was driving under the influence.

Payton v. New York: The Fourth Amendment prohibits warrantless, nonconsensual entry into a suspect’s home to make a routine felony arrest. Officers must have a warrant to enter a home unless exigent circumstances exist.

Chimel v. California: Incident to a lawful custodial arrest, officers may search only the arrestee’s person and the area within their immediate control (i.e., where the arrestee could grab a weapon or destroy evidence). A broader search of the home requires a warrant.

Kentucky v. King: Police may rely on the exigent circumstances exception to enter a home without a warrant even if their lawful conduct created the exigency, as long as they did not engage in or threaten to engage in unconstitutional conduct.

Home Searches

Warrants & Exigency: Warrants are required to enter homes unless exigent circumstances exist.
Warrant must have:
1. Issued by a neutral and detached magistrate/judicial officer.
2. Oath or affirmation supporting the allegations.
3. Particular description of the place to be searched and the things to be seized.

Seizure and Search of Vehicle and Effects

California v. Carney: The automobile exception to the Fourth Amendment’s warrant requirement applies to mobile homes (e.g., motor homes) if they are readily mobile and being used in a way that is not primarily residential. Police may search such a vehicle without a warrant if they have probable cause.

Arizona v. Gant: Police may search a vehicle incident to a recent occupant’s arrest only if:

the arrestee is within reaching distance of the vehicle at the time of the search, or
it is reasonable to believe the vehicle contains evidence relevant to the crime of arrest.

California v. Acevedo: Police may search a container within a vehicle without a warrant if they have probable cause to believe the container holds contraband or evidence. The automobile exception allows search of the entire vehicle, including containers, based on probable cause.

Wyoming v. Houghton: If police have probable cause to search a vehicle, they may also search personal belongings (like purses or bags) of passengers found within the vehicle that might conceal the object of the search.

Colorado v. Bertine: Police may conduct a warrantless inventory search of a vehicle lawfully in police custody as long as the search is conducted according to standardized procedures and not a pretext for investigation.

Riley v. California: Police must obtain a warrant before searching the digital contents of a cell phone seized incident to arrest.

Automobiles and Related Rules

Automobiles: Due to their mobility, vehicles can be searched without a warrant if there is probable cause.

Purpose: Reduced expectation of privacy in vehicles; includes searches of containers and compartments.
Officers may not search a vehicle’s passenger compartment unless:
1. the arrestee is unsecured and within reaching distance, or
2. it’s reasonable to believe the vehicle contains evidence related to the arrest.
Locked Containers:
- California v. Acevedo: Probable cause allows searches of locked containers in vehicles.
- United States v. Chadwick: Containers outside of vehicles (e.g., footlockers) require a warrant.
Passengers’ Rights: Passengers in stopped vehicles are considered seized and have standing to challenge the legality of the stop.

Stop and Frisk (Terry)

Terry v. Ohio: Police may stop and briefly detain a person for investigative purposes if they have reasonable suspicion that the person is involved in criminal activity. They may also frisk for weapons if they have reason to believe the person is armed and dangerous.

Kansas v. Glover: An officer may reasonably suspect that the registered owner of a vehicle is the driver when there is no information to the contrary, thus justifying a traffic stop under the Fourth Amendment.

Florida v. J.L.: An unverified anonymous tip about a person carrying a gun, without independent corroboration, does not justify a stop and frisk.

Florida v. Royer: Moving a suspect to a new location without probable cause transforms a Terry stop into an arrest, which requires probable cause.

U.S. v. Drayton: Officers are not required to inform individuals of their right to refuse consent during consensual encounters on buses under the Fourth Amendment.

Brendlin v. California, 551 U.S. 249 (2007): Passengers in a vehicle are seized during a traffic stop and thus have standing to challenge the constitutionality of the stop under the Fourth Amendment.

Rodriguez v. U.S.: Prolonging a traffic stop beyond the time needed to handle the stop’s mission without reasonable suspicion violates the Fourth Amendment.

Schneckloth v. Bustamonte: Voluntariness of consent to search is judged based on the totality of the circumstances; officers are not required to inform individuals they have a right to refuse.

State v. Daniel (Tenn.): In Tennessee, a seizure occurs when, under the totality of the circumstances, a reasonable person would not feel free to leave, similar to federal Fourth Amendment standards.

Stop-and-Frisk Doctrines

Plain View Doctrine: Allows officers to seize evidence without a warrant if it is in plain view during a lawful presence. Requirements: officer must be lawfully present and the incriminating nature of the item must be immediately apparent.

Plain Feel Doctrine: Officers may seize items during a frisk if the incriminating nature of the item is immediately apparent. Officers cannot manipulate objects to determine their nature.

Duration & Scope of Stops: Stops must be brief and limited to the time necessary to confirm or dispel the suspicion. Rodriguez v. U.S. holds that extended stops without additional justification violate the Fourth Amendment.

Levels of Police-Citizen Encounters:

Consensual encounter: No justification required; individual is free to leave.
Investigatory detention (Terry stop): Requires reasonable suspicion; limited in duration and scope.
Arrest: Requires probable cause.

Consent Searches

Georgia v. Randolph: A warrantless search of a shared residence is invalid when one physically present occupant objects to the search, even if another occupant consents.

State v. Berrios (Tenn.): Under Tennessee law, consent to search must be freely and voluntarily given under the totality of the circumstances, and the prosecution must prove voluntariness by clear and positive testimony.

Consent Rules

Consent Searches: If a person voluntarily consents to a search, a warrant is unnecessary.

Requirements: Consent must be given freely without coercion; scope of the search is limited to what is agreed upon.
Third-Party Consent: Permissible if the person has apparent authority (roommate, spouse).
Consent must not be coerced but can occur without the person’s knowledge that they have a right to refuse.

Scope of the Exclusionary Rule

Wong Sun v. U.S.: Evidence obtained as the “fruit of the poisonous tree” — meaning derived from illegal government action — must be excluded, unless the connection to the illegal act is sufficiently attenuated.

Brown v. Illinois: Miranda warnings do not automatically purge the taint of an unlawful arrest; courts must consider factors like temporal proximity, intervening circumstances, and purpose and flagrancy of the police misconduct to determine attenuation.

New York v. Harris: A statement made outside the home after a warrantless but probable-cause-supported arrest inside the home is admissible under the Fourth Amendment, even though the arrest itself violated Payton v. New York.

Utah v. Strieff: Discovery of a valid arrest warrant during an unlawful investigatory stop attenuates the connection between the illegal stop and the discovery of evidence, making the evidence admissible.

Murray v. U.S.: Under the independent source doctrine, evidence initially discovered during or as a result of an unlawful search may still be admissible if it is later obtained independently by lawful means.

Nix v. Williams: Under the inevitable discovery doctrine, illegally obtained evidence is admissible if the prosecution can show by a preponderance of the evidence that the information would have been inevitably discovered through lawful means.

Hudson v. Michigan: A violation of the knock-and-announce rule does not require suppression of the evidence found during the search; exclusion is not a remedy for every Fourth Amendment violation.

Attenuation and Doctrines

Attenuation factors: Evidence obtained after illegal police actions can be admitted if the connection to the illegality is sufficiently remote.

Temporal proximity between illegality and evidence discovery.
Presence of intervening circumstances.
Purpose and flagrancy of police misconduct.

Lay terms:

Time elapsed.
Intervening events.
Purpose of the misconduct.

Inevitable Discovery Doctrine: Permits the admission of unlawfully obtained evidence if the prosecution proves that the evidence would have been discovered inevitably by lawful procedures.

Independent Source Doctrine: Permits the admission of evidence discovered during an unlawful search if it is later obtained independently through a valid warrant that is not influenced by the initial illegal search.