An Overview of the Fourth Amendment: Protections & Exclusions

Probably one of the most litigated legal issues in the criminal justice system, the Fourth Amendment of the U.S. Constitution reads:

“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

During colonial times, British authorities would issue “general warrants” which would enable them to search anywhere without probable cause. Thus, the Founding Fathers included this right in the Constitution to protect themselves and future generations from such insidious practices. In other words, this Amendment protects an individual’s privacy in both their house, papers, and belongings. Without a warrant supported by probable cause, this privacy cannot be invaded. As with any rule, there are exceptions to this rule; however, the main purpose is to make sure law enforcement officials have sufficient evidence before they invade an individual’s privacy.

Search Warrant

A search warrant must be issued by a judge or magistrate in order for law enforcement to search or seize anything or anyone. The warrant must specifically list the basis for which law enforcement’s probably cause is based. Further, there must be a specific description of a place, object, or individual that will be searched and/or seized. For example, suppose the police received a tip that a ranch stored weapons. The police applied for a warrant to search the ranch and it was approved. However, the warrant did not describe the items to be seized. The Supreme Court held that because this warrant did not describe what was to be searched, the warrant was invalid under the Fourth Amendment. [Groh v. Ramirez, 540 US 551 (2004)]

The Supreme Court of the United States has established that probable cause on a warrant is met when the facts and circumstances of the case along with “reasonably trustworthy information” are sufficient to lead one to believe that a crime had been or is being committed. [Brinegar v. United States, 338 U.S. 160 (1949)] All of the facts must be examined in totality in order to determine if probable cause exists. For example, when relying on an informant’s tip, the Supreme Court held that the totality of the circumstances must be examined, including the veracity of the informant, their reliability, the basis of their knowledge, as well as any corroborating evidence the police have. [Illinois v. Gates, 462 US 213 (1983)]

If a search is performed without a warrant, for an individual to claim that their Fourth Amendment right was violated, the individual must prove that they had a legitimate expectation of privacy. Justice Harlan established the two-part test to determine if a legitimate interest in privacy exists. [Katz v. United States, 389 US 347 (1967); Smith v. Maryland, 442 US 735 (1979)].

  1. 1. Actual Expectation of Privacy: For the first part, the individual must establish that they have an expectation of privacy. This expectation must be concrete, so the individual must explain why such privacy was anticipated.
  1. 2. Reasonable Expectation: The second part denotes that the expectation of that privacy must be one that society would recognize as a reasonable expectation.

For example, most people expect privacy in their home – and that is a reasonable expectation. This goes back to the old notion that “a man’s house is his castle.” Alternatively, the Supreme Court has held that the installation of a GPS on a vehicle without a warrant constitutes a violation of the Fourth Amendment. [United States v. Jones, 565 U.S. 400 (2012). Thus, a warrantless search where one would reasonably expect privacy is a violation of the Fourth Amendment, unless the situation satisfies one of the exceptions to the warrant requirement.

There are a few exceptions to the warrant requirement. Where these circumstances exist, courts have held the search or seizure did not constitute a violation of an individual’s Fourth Amendment right. The following lists the most prevalent exceptions:

1. Consent: Consent to a search is an exception to the warrant requirement. This consent must be given by an individual voluntarily and not as the result of any coercion. [Schneckloth v. Bustamonte, 412 U.S. 218 (1973)]. Consent is a question of fact and all the facts must be examined in order to determine the voluntariness of consent. For example, the Supreme Court has held that the Fourth Amendment was not violated when three officers boarded a bus during a routine drug interdiction effort and asked to check the defendant’s bag because the defendant gave voluntary consent. [United States v. Drayton, 536 U.S. 194 (2002)] In regard to a home setting, the Supreme Court has held that if one occupier gives consent, but the co-occupant does not, then police cannot enter the premises without a warrant. [Georgia v. Randolph, 547 U.S. 103 (2006)] This is based on long understandings of social expectations.

2. Plain view doctrine: During a warrantless search, the Court has adopted the “plain view doctrine” which denotes that an object in plain view can be seized, despite police having no warrant. This reasoning goes back to the two-part test on whether there is a reasonable expectation of privacy. Logically, if something is left in plain view, one did not expect to have a privacy interest. For example, when police searched a suspect’s house for stolen items connected to a robbery, the Court held that police did not violate the Fourth Amendment when they seized various weapons connected with the robbery because they were in plain view. [Horton v. California, 496 U.S. 128 (1990)]

3. Exigent circumstances: Courts have held that under extreme or emergency situations a warrant is not needed. If evidence found during these exigent circumstances could be “tied to and justified by the exigencies”, the warrantless search would be “excused.” [Warden, Maryland Penitentiary v. Hayden, 387 U.S. 294 (1967)].

    • Hot Pursuit: For example, suppose a suspect from an armed robbery ran into a house. When the police arrived, they entered, found the suspect, and arrested him. During the arrest, they found a weapon, ammunition, and some clothes that matched the description of the robber. These are the facts of a Supreme Court case in which the Court held that this exigent circumstance of “hot pursuit” permitted the introduction of the evidence at trial, despite the police not having a warrant. Further, the need to protect the police from any weapons that the suspect could have reached for justified the warrantless search. [Warden, Maryland Penitentiary v. Hayden, 387 U.S. 294 (1967) Without such exigent circumstances, police cannot search premises or arrest an individual without a warrant. [Payton v. New York, 445 U.S. 573 (1980)]


    • Imminent Danger: If there is reasonable evidence in which officers believe that someone is injured or in immediate danger, they may enter the premises without a warrant, as such imminent danger satisfies the criteria of an exigent circumstance. For example, when officers were called to a home in response to a noisy party, they witnessed a fight inside a house, where someone was injured. The police entered the house without a warrant, stopped the fight, and arrested some of the individuals at the party. The Supreme Court held that the police witnessed the fight and thus had reason to believe that someone was injured and perhaps needed an ambulance. Therefore, the entry into the home without a warrant did not violate the Fourth Amendment. [Brigham City v. Stuart, 547 US 398 (2006)]. Similarly, the Court held that police’s warrantless entry into a home did not violate the Fourth Amendment when the police officer heard screaming and saw blood on a truck outside the home and a cut on the defendant’s hand when he opened the door. [Michigan v. Fisher, 558 U.S. 45 (2009).]

    4. Automobile searches: Searching a car without a warrant is another exception to the warrant requirement. The reasoning behind such a rule is that it is not feasible to procure a warrant to search a car because a car can be easily moved before one can execute the warrant. [Carroll v. United States, 267 U.S. 132 (1925)] This has even been extended to mobile homes. [California v. Carney, 471 U.S. 386 (1985)] Further, the Court has upheld the search of a container in a car where police had probable cause to believe that the container contained marijuana. [California v. Acevedo, 500 U.S. 565 (1991)] However, when a car is parked next to an individual’s home, the automobile exception does not apply and a warrant is needed to search the car. [Collins v. Virginia, 138 S. Ct. 1663)]

    5. Searches incident to arrest: A warrantless search during a lawful arrest is not a violation of the Fourth Amendment. During a lawful arrest, law enforcement must be able to search the person to remove any weapons they may have on their person or in the vicinity. This helps protect law enforcement from harm. Without such a search, the police are put at risk. However, such searches must be reasonable. As an example, suppose an officer lawfully arrests an individual for burglary, but then searches the house and finds evidence linking the individual to the burglary. The Supreme Court held that this violated the Fourth Amendment because the search went beyond searching the area within the arrestee’s “immediate control” and thus was unreasonable. [Chimel v. California, 395 U.S. 752 (1969)] Similarly, the Court has also held that a traffic stop and the issuance of a citation does not permit a warrantless search as a traffic stop is a minimal intrusion and no further evidence existed that the officer was somehow in danger. [Knowles v. Iowa, 525 U.S. 113 (1998)]


      A warrant is also generally required to arrest (or seize) an individual. However, there is a long-standing practice of arresting an individual without a warrant if it is pursuant to a congressional statute. For example, the Supreme Court upheld an arrest as lawful when a police arrested an individual in public without a warrant based on information from an informant that he had stolen credit cards because the arrest was authorized under a legislative statute. [United States v. Watson, 423 U.S. 411 (1976]. The Court further held that such an arrest can be upheld only if there is probable cause that the suspect committed a felony. However, a warrant is required to enter someone’s home and arrest them. Without a warrant, such an arrest violates the Fourth Amendment. [Payton v. New York, 445 U.S. 573 (1980)]

      A seizure takes place when law enforcement, whether by actual force or by a show of their authority, restrain the liberty of an individual in a way that makes that individual believe that they are not free to leave. [United States v. Mendenhall, 446 U.S. 544 (1980); California v. Hodari D., 499 U.S. 621 (1991)] For example, the Supreme Court held that a seizure was lawful when law enforcement boarded a bus and asked to search the bags of the passengers because a reasonable person would have felt free to leave or refuse the request. [United States v. Drayton, 536 U.S. 194 (2002)] The Court held the reasonable person standard presumes an innocent person.

      Stop & Frisk

      Apart from warrants to search a place or arrest an individual, police also have the authority to stop an individual on the street and search them. In a landmark Supreme Court case, the Court held that if an officer observes “unusual conduct” that leads him to reasonably believe that “criminal activity may be afoot”, they can perform a limited search. [Terry v. Ohio, 392 U.S. 1 (1968)] This is referred to as a “Terry stop” where a police officer can “stop and frisk” an individual for weapons if the police reasonably believe that some type of criminal activity is occurring. The standard is not probable cause that criminal activity is “afoot” but rather a lesser standard called reasonable suspicion. Reasonableness of the stop depends on both the view of the circumstances as perceived by the police officer and the facts known to him as well as the police officer’s safety.

      Exclusionary Rule

      The exclusionary rule is applied to any search or seizure deemed in violation of the Fourth Amendment. The “exclusionary rule” was invented by the Supreme Court in 1914. The Court was faced with a situation where law enforcement (without a warrant) took letters and envelopes from the defendant’s home to use against him in a criminal trial. It reasoned that the Fourth Amendment would have no meaning if evidence from a warrantless search could be used against an individual by the prosecution in a criminal case. Thus, they invented the exclusionary rule which mandates that the evidence found during an unlawful search be suppressed, or not used against the defendant. [Weeks v. United States, 232 U.S. 383 (1914)] This rule was later ruled to be applicable in state criminal proceedings. [Mapp v. Ohio, 367 U.S. 643 (1961)]

      The exclusionary rule is a controversial topic in criminal law – a double-edged sword. On one hand, it protects against government intrusion and malfeasance. Such a rule acts as an incentive for law enforcement to acquire a warrant when needed, or risk having the evidence inadmissible. However, on the other hand, as Judge Benjamin Cardozo famously said, ““The criminal is to go free because the constable has blundered.” Others believe that because the exclusionary rule suppresses evidence, individuals who really committed crimes then cannot be prosecuted and thus escape justice.

      Over the years, the exceptions to the exclusionary rule have evolved. These rules recognize that an individual’s Fourth Amendment right was violated by the warrantless search. However, due to the circumstances surrounding the case, the evidence can still be used against the defendant at trial.

      1. Police Negligence: The Supreme Court has held that when law enforcement acts negligently, but not recklessly, the evidence against a defendant is still admissible at trial. For example, the Supreme Court held that when the police arrested an individual pursuant to a warrant that was recalled due to an administrative error, the evidence found during a search of the individual’s car was admissible because the police acted only negligently and reasonably believed that an arrest warrant existed. [Herring v. United States, 555 U.S. 135 (2009)]

      2. Independent Source Doctrine: Another exception to the exclusionary rule is the independent source doctrine. Under this exception, any evidence, although obtained in violation of the Fourth Amendment, can be used at trial, if an “independent source” exists where the evidence could lawfully be obtained. For example, where police officers entered a warehouse unlawfully and observed drugs, but left and later got a warrant for the warehouse, the Supreme Court permitted the evidence gathered at trial despite the unlawful first search as the second search was performed with a lawfully obtained warrant. [Murray v. United States, 487 U.S. 533 (1988)]

      3. Inevitable Discovery: Under the inevitable discovery doctrine, unlawfully obtained evidence can be used at trial if the prosecution can provide evidence that the information unlawfully obtained would have eventually been discovered lawfully. [Nix v. Williams, 467 U.S. 431 (1984)] The use of that evidence does not diminish the integrity of the criminal justice system because it would have been discovered eventually, and thus the exclusionary rule is not warranted in these situations.


        The Founding Fathers included the Fourth Amendment in the United States Constitution to guard against intrusion of the right to privacy and to protect against government misconduct and abuses. Over the years, it has been defined, clarified, and in some instances contracted. These requirements have served to better guide law enforcement in protecting society from danger while increasing the privacy protections of individuals. It is an integral part of the U.S. criminal justice system. footer logo 5