Fourth Amendment

The Fourth Amendment (Amendment IV) to the United States Constitution is the part of the Bill of Rights which guards against unreasonable searches and seizures, along with requiring any warrant to be judicially sanctioned and supported by probable cause. It was adopted as a response to the abuse of thewrit of assistance, which is a type of general search warrant, in the American Revolution. Search and seizure (including arrest) should be limited in scope according to specific information supplied to the issuing court, usually by a law enforcement officer, who has sworn by it. The Fourth Amendment applies to the states by way of the Due Process Clause of the Fourteenth Amendment.
TextThe 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.

History of adoption

English law

Like many other areas of American law, the Fourth Amendment finds its roots in English legal doctrine. Sir Edward Coke, in Semayne's case (1604), famously stated: "The house of every one is to him as his castle and fortress, as well for his defence against injury and violence as for his repose." Semayne's Caseacknowledged that the King did not have unbridled authority to intrude on his subjects' dwellings but recognized that government agents were permitted to conduct searches and seizures under certain conditions when their purpose was lawful and a warrant had been obtained. 

The 1760s saw a growth in the intensity of litigation against state officers, who, using general warrants, conducted raids in search of materials relating to John Wilkes' publications attacking both government policies and the King himself. The most famous of these cases involved John Entick, whose home was forcibly entered by the King's Messenger Nathan Carrington, along with others, pursuant to a warrant issued by George Montagu-Dunk, 2nd Earl of Halifax authorizing them “to make strict and diligent search for . . . the author, or one concerned in the writing of several weekly very seditious papers intitled, ‘The Monitor or British Freeholder, No 257, 357, 358, 360, 373, 376, 378, and 380,’″ and seized printed charts, pamphlets and other materials. In the resulting case, Entick v. Carrington (1765), Charles Pratt, 1st Earl Camden ruled that the search and seizure was unlawful as the warrant authorized the seizure of all of Entick's papers, not just the criminal ones and the warrant lacked probable cause to even justify the search. Entick established the English precedent that the executive is limited in intruding on private property by common law. 

Colonial America

In Colonial America, legislation was explicitly written to enforce English revenue gathering policies on customs. Until 1750, all handbooks for justices of the peace, the issuers of warrants, contained or described only general warrants. William Cuddihy, Ph.D. in his dissertation entitled The Fourth Amendment: Origins and Original Meaning,  claims there existed a "colonial epidemic of general searches." According to him, until the 1760s, a "man's house was even less of a legal castle in America than in England" as the authorities possessed almost unlimited power and little oversight.

In 1756, the colony of Massachusetts enacted legislation that barred the use of general warrants. This represented the first law in American history curtailing the use of seizure power. Its creation largely stemmed from the great public outcry over the Excise Act of 1754, which gave tax collectors unlimited powers to interrogate colonists concerning their use of goods subject to customs and permitted the use of a general warrant known as a writ of assistance, allowing them to search the homes of colonists and seize “prohibited and uncustomed” goods. 

A crisis erupted over the writs of assistance on December 27, 1760 when the news of King George II's October 23 death arrived in Boston. All writs automatically expired six months after the death of the King and would have had to be re-issued under the name of the new King, George III, to remain valid. 

In mid-January 1761, a group of over 50 merchants represented by James Otis, petitioned the court to have hearings on the issue. During the five hour hearing on February 23, 1761, Otis vehemently denounced English colonial policies, including their sanction of general warrants and writs of assistance.  John Adams, who was present in the courtroom when Otis spoke, viewed these events as "the spark in which originated the American Revolution.”  However, the court ruled against Otis. 

Because of the name he had made for himself in attacking the writs, Otis was elected to the Massachusetts colonial legislature and helped pass legislation requiring that special writs of assistance be “granted by any judge or justice of the peace upon information under oath by any officer of the customs” and barring all other writs. The governor overturned the legislation, finding it contrary to British law and parliamentary sovereignty. 

Seeing the danger general warrants presented, the Virginia Declaration of Rights explicitly forbade the use of general warrants. This prohibition became precedent for the Fourth Amendment: 

That general warrants, whereby any officer or messenger may be commanded to search suspected places without evidence of a fact committed, or to seize any person or persons not named, or whose offense is not particularly described and supported by evidence, are grievous and oppressive and ought not to be granted. 

Article XIV of the Massachusetts Declaration of the Rights written by John Adams and enacted in 1780 as part of the Massachusetts Constitution added the requirement that all searches must be “reasonable” and served as the basis for the language of the Fourth Amendment: 

Every subject has a right to be secure from all unreasonable searches, and seizures of his person, his houses, his papers, and all his possessions. All warrants, therefore, are contrary to this right, if the cause or foundation of them be not previously supported by oath or affirmation; and if the order in the warrant to a civil officer, to make search in suspected places, or to arrest one or more suspected persons, or to seize their property, be not accompanied with a special designation of the persons or objects of search, arrest, or seizure: and no warrant ought to be issued but in cases, and with the formalities, prescribed by the laws. 

Applicability

The Fourth Amendment has been held to mean that generally a warrant must be judicially sanctioned for a search or an arrest. In order for such a warrant to be considered reasonable, it must be supported by probable cause and be limited in scope according to specific information supplied by a person (usually a law enforcement officer) who has sworn by it and is therefore accountable to the issuing court. However, a dissenting school of thought often found in the opinions of Justice Antonin Scalia is that searches must simply be "reasonable," and the warrant requirement has been overly emphasized.

The Fourth Amendment applies to governmental searches and seizures, but not those done by private citizens or organizations who are not acting on behalf of a government. The Bill of Rightsoriginally only restricted the federal government. However, in Mapp v. Ohio, 367 U.S. 643 (1961), the Supreme Court ruled that the Fourth Amendment applies to the states by way of the Due Process Clause of the Fourteenth Amendment. Moreover, all state constitutions contain an analogous provision. 

Federal jurisdiction regarding criminal law was narrow, until the late 19th century when the Interstate Commerce Act and Sherman Antitrust Act were passed. As federal criminal jurisdiction expanded to include other areas, such as narcotics, more questions about the Fourth Amendment came to the Supreme Court. 

The Supreme Court ruled that some searches and seizures may violate the reasonableness requirement under the Fourth Amendment, even if a warrant is supported by probable cause and is limited in scope. Conversely, the Court has approved routine warrantless seizures, for example "where there is probable cause to believe that a criminal offense has been or is being committed." Thus, the reasonableness requirement and the warrant requirement are somewhat different.

The reasonableness requirement applies not just to a search in combination with a seizure, but also to a search without a seizure, as well as to a seizure without a search. 

Definition of "search"

A threshold question in Fourth Amendment jurisprudence is whether a search has occurred. If no search occurred, then the Fourth Amendment does not apply.

In Katz v. United States, 389 U.S. 347 (1967), the Supreme Court ruled that a search occurs when 1) a person expects privacy in the thing searched and 2) society believes that expectation isreasonable.

In Katz, the Supreme Court ruled that a search had occurred when the government wiretapped a telephone booth.  The Court's reasoning was that 1) Charles Katz expected that his phonebooth conversation would not be broadcast to the wider world and 2) society believes that expectation is reasonable.

In United States v. Jones, 565 U. S. ____ (2012), the Supreme Court ruled that, in addition to the Katz standard, a search occurs when law enforcement trespasses on the searched person's property. In Jones, law enforcement officers had attached a GPS device on a car's exterior without Antoine Jones's consent. The Court concluded that Jones was a bailee to the car, because the car's owner had regularly permitted him to use the car, and so had a property interest in the car. 

Stop and frisk

Under Terry v. Ohio 392 U.S. 1 (1968), law enforcement officers are permitted to conduct a limited warrantless search on a level of suspicion less than probable cause under certain circumstances. In Terry, the Supreme Court ruled that when a police officer witnesses "unusual conduct" that leads that officer to reasonably believe "that criminal activity may be afoot", that the suspicious person has a weapon and that the person is presently dangerous to the officer or others, the officer may conduct a "pat-down search" (or "frisk") to determine whether the person is carrying a weapon. To conduct a frisk, officers must be able to point to specific and articulatory facts which, taken together with rational inferences from those facts, reasonably warrant their actions. A vague hunch will not do. Such a search must be temporary and questioning must be limited to the purpose of the stop (e.g., officers who stop a person because they have reasonable suspicion to believe that the person was driving a stolen car, cannot, after confirming that it is not stolen, compel the person to answer questions about anything else, such as the possession of contraband). 

Seizure

The Fourth Amendment proscribes unreasonable seizure of any person, person's home (including its curtilage) or personal property without a warrant. A seizure of property occurs when there is "some meaningful interference with an individual's possessory interests in that property",  such as when police officers take personal property away from an owner to use as evidence, or when they participate in an eviction. The Amendment also protects against unreasonable seizure of their persons, including a brief detention. 

A seizure does not occur just because the government questions an individual in a public place. The exclusionary rule would not bar voluntary answers to such questions from being offered into evidence in a subsequent criminal prosecution. The person is not being seized if his freedom of movement is not restrained. The government may not detain an individual even momentarily without reasonable, objective grounds, with few exceptions. His refusal to listen or answer does not by itself furnish such grounds. 

A person is seized within the meaning of the Fourth Amendment only when, by means of physical force or show of authority, his freedom of movement is restrained and, in the circumstances surrounding the incident, a reasonable person would believe that he was not free to leave.  As long as the police do not convey a message that compliance with their requests is required, the courts will usually consider the police contact to be a "citizen encounter" which falls outside the protections of the Fourth Amendment.  If a person remains free to disregard questioning by the government, there has been no intrusion upon the person's liberty or privacy under the Fourth Amendment — there has been no seizure. 

Exceptions

The government may not detain an individual even momentarily without reasonable and articulable suspicion, with a few exceptions. In Delaware v. Prouse, 440 U.S. 648 (1979), the Supreme Court ruled that, absent articulable and reasonable suspicion that a motorist is unlicensed or that an automobile is not registered, or that either the vehicle or an occupant is otherwise subject to seizure for violation of law, stopping an automobile and detaining the driver in order to check his driver's license and the registration of the automobile are unreasonable.

Where society's need is great and no other effective means of meeting the need is available, and intrusion on people's privacy is minimal, certain discretionless checkpoints toward that end may briefly detain motorists. In United States v. Martinez-Fuerte, 428 U.S. 543 (1976), the Supreme Court allowed discretionless immigration checkpoints. In Michigan Dept. of State Police v. Sitz, 496 U.S. 444 (1990), the Supreme Court allowed discretionless sobriety checkpoints. In Illinois v. Lidster, 540 U.S. 419 (2004), the Supreme Court allowed focused informational checkpoints. However, in City of Indianapolis v. Edmond, 531 U.S. 32 (2000), the Supreme Court ruled that discretionary checkpoints or general crime-fighting checkpoints are not allowed.

Another exception is at borders and ports of entry.

Roadblocks may be used to capture a particular fleeing criminal or locate a bomb. 

Arrest

When a person is arrested and taken into police custody, they have been seized (e.g., a reasonable person who is handcuffed and placed in the back of a police car would not think they were free to leave). A person subjected to a routine traffic stop on the other hand, has been seized, but is not "arrested" because traffic stops are a relatively brief encounter and are more analogous to a Terry stop than to a formal arrest.  A police officer does not have the authority to arrest someone for refusing to identify himself when he is not suspected of committing a crime, unless state law says otherwise. A search incidental to an arrest that is not permissible under state law does not violate the Fourth Amendment, if the arresting officer has probable cause. 

Arrest by a citizen

The Fourth Amendment does not apply to a seizure or an arrest by private citizens. However, many states have passed laws that regulate the specific circumstances in which a private citizen may arrest another. Typically, a private person can make an arrest when: (1) a misdemeanor amounting to a public nuisance is being committed; or (2) a felony has been committed, and the arresting citizen has reasonable cause to believe that the person arrested committed it.

Warrant

Under the Fourth Amendment, law enforcement must receive written permission from a court of law, or otherwise qualified magistrate, to lawfully search and seize evidence while investigatingcriminal activity. A court grants permission by issuing a writ known as a warrant. A search or seizure is generally unreasonable and unconstitutional if conducted without a valid warrant  and the police must obtain a warrant whenever practicable. Searches and seizures without a warrant are not considered unreasonable if one of the specifically-established and well-delineatedexceptions to the warrant requirement applies. 

Probable cause

 

When police conduct a search, the amendment requires that the warrant establishes probable cause to believe that the search will uncover criminal activity or contraband. They must have legally sufficient reasons to believe a search is necessary. In Carroll v. United States, 267 U.S. 132 (1925), the Supreme Court stated that probable cause to search is a flexible, common-sense standard. To that end, the Court ruled in Dumbra v. United States, 268 U.S. 435 (1925), that the term probable cause means "less than evidence that would justify condemnation," reiteratingCarroll's assertion that it merely requires that the facts available to the officer would "warrant a man of reasonable caution" in the belief that specific items may be contraband or stolen property or useful as evidence of a crime. It does not demand any showing that such a belief be correct or more likely true than false. A "practical, non-technical" probability that incriminating evidence is involved is all that is required.  In Illinois v. Gates, 462 U.S. 213 (1983), the Supreme Court ruled that the reliability of an informant is to be determined based on the "totality of the circumstances."

At common law, a police officer could arrest an individual if that individual committed a misdemeanor in the officer's presence or if the officer had probable cause to believe that the individual committed a felony. For misdemeanors, probable cause to believe that a wrongdoer committed a misdemeanor is not sufficient for an arrest—the police officer has to actually witness the misdemeanor. 

The standards of probable cause differ for an arrest and a search. The government has a probable cause to make an arrest when "the facts and circumstances within their knowledge and of which they had reasonably trustworthy information" would lead a prudent person to believe that the arrested person had committed or was committing a crime.  Probable cause to arrest must exist before the arrest is made. Evidence obtained after the arrest may not apply retroactively to justify the arrest. 

Exclusionary rule

One way courts enforce the Fourth Amendment is through the use of the exclusionary rule. The rule provides that evidence obtained through a violation of the Fourth Amendment is generally notadmissible by the prosecution during the defendant's criminal trial.

 

The Court adopted the exclusionary rule in Weeks v. United States, 232 U.S. 383 (1914), prior to which all evidence, no matter how seized, could be admitted in court. Additionally, inSilverthorne Lumber Co. v. United States, 251 U.S. 385 (1920) and Nardone v. United States, 308 U.S. 338 (1939), the Court ruled that tips resulting from illegally obtained evidence are also inadmissible in trials as "fruit of the poisonous tree". The rule serves primarily to deter police officers from willfully violating a suspect's Fourth Amendment rights. The rationale behind the exclusionary rule is that if the police know evidence obtained in violation of the Fourth Amendment cannot be used to convict someone of a crime, they will not violate it. In Wolf v. Colorado, 338U.S. 25 (1949), the Court rejected incorporation of the exclusionary rule by way of the Fourteenth Amendment. Later, in Mapp v. Ohio, 367 U.S. 643 (1961), the Court explicitly overruled Wolfand made the Fourth Amendment (including the exclusionary rule) applicable in state proceedings as an essential part of criminal procedure.

Limitations

In United States v. Calandra, 414 U.S. 338 (1974), the Supreme Court ruled that grand juries may use allegedly illegally obtained evidence in questioning witnesses because "the damage to that institution from the unprecedented extension of the exclusionary rule outweighs the benefit of any possible incremental deterrent effect."  The issue of illegality of search should be adjudged in a subsequent proceeding, after the defendant has been indicted. In United States v. Leon, 468 U.S. 897 (1984), the Supreme Court, applying the "good faith" rule, ruled that evidence seized by officers relying in good faith on a warrant was still admissible, even though the warrant was later found to be defective. Evidence would be excluded, however, if an officer dishonestly or recklessly prepared an affidavit to seek a warrant, the issuing magistrate abandoned his neutrality, or the warrant lacked sufficient particularity. 

The Leon case applies only to search warrants. The Supreme Court ruled in Arizona v. Evans, 514 U.S. 1 (1995) and Herring v. United States (2009), that the exclusionary rule does not apply to evidence found due to negligence regarding a government database, as long as the arresting police officer relied on that database in "good faith" and that the negligence was not pervasive. In Davis v. United States, 131 S.Ct. 2419 (2011), the Supreme Court ruled that the exclusionary rule does not apply to a Fourth Amendment violation resulting from a reasonable reliance on binding appellate precedent.  To what extent the "good faith" exception applies to warrantless seizures in other contexts remains unclear.

The rule has been held not to apply in the following circumstances:

• probation or parole revocation hearings; tax hearings; 
• deportation hearings; 
• military discharge proceedings;  child protective proceedings; 
• sentencing hearings; 
• evidence seized from a common carrier; 
• evidence collected by U.S. Customs agents;   
• evidence seized outside the United States; 
• evidence illegally seized by a "private actor" (i.e., not a governmental employee);  
• illegally seized evidence used to impeach the defendant's testimony. 

Under Rakas v. Illinois, 439 U.S. 128 (1978), a defendant has standing to object to the admission of unconstitutionally seized evidence only if such seizure violated that defendant's Fourth Amendment rights. In other words, a defendant may not assert another person's rights.

In Rakas, the Court ruled that a passenger in a car which he does not own has standing to contest the stop of the car and a search of *his* person, but he usually lacks standing to contest a search of the car. He would have standing to challenge the search of the car, if he is the owner of that car. However, that rule was modified by Brendlin v. California, 551 U.S. 249 (2007), in which the Court ruled that all occupants of a car are "seized" for purposes of the Fourth Amendment during a traffic stop, not just the driver. Therefore, a passenger in a vehicle subject to a traffic stop is thereby "detained" for purposes of the Fourth Amendment, thus allowing the passenger to contest the legality of the traffic stop.

In Segura v. United States, 468 U.S. 796 (1984), the Supreme court ruled that evidence illegally found without a search warrant is admissible if the evidence is later found and legally seized based on information independent of the illegal search.

In Nix v. Williams, 467 U.S. 431 (1984), the Supreme Court ruled that evidence illegally seized without a search warrant is admissible if the prosecution can prove the evidence would have been found and seized by legal means not based on evidence or information illegally seized.

Exceptions to the warrant requirement

Courts have developed a number of exceptions to the warrant requirement:

Consent

If a party gives consent to a search, a warrant is not required, even if the party is unaware of their right to refuse to cooperate. There are exceptions and complications to the rule, including the scope of the consent given, whether the consent is voluntarily given, and whether an individual has the right to consent to a search of another's property. 

Plain view

If an officer is lawfully present, he may seize objects that are in "plain view". However, the officer must have had probable cause to believe that the objects are contraband. 

Open fields

Similarly, "open fields" such as pastures, open water, and woods may be searched without a warrant, on the ground that conduct occurring therein would have no reasonable expectation of privacy.

 

The doctrine was first articulated by the Supreme Court in Hester v. United States, 265 U.S. 57 (1924), which stated that “the special protection accorded by the Fourth Amendment to the people in their ‘persons, houses, papers, and effects,’ is not extended to the open fields." The decision was rendered on the ground that "open fields are not a 'constitutionally protected area' because they cannot be construed as "persons, houses, papers, [or] effects.

 

In Oliver v. United States, 466 U.S. 170 (1984), the police ignored a "no trespassing" sign and a fence, trespassed onto the suspect's land without a warrant, followed a path for hundreds of feet, and discovered a field of marijuana. The Supreme Court ruled that no search had taken place, because there was no privacy expectation regarding an open field:

open fields do not provide the setting for those intimate activities that the Amendment is intended to shelter from government interference or surveillance. There is no societal interest in protecting the privacy of those activities, such as the cultivation of crops, that occur in open fields. 

Curtilage

While open fields are not protected by the Fourth Amendment, the curtilage, or outdoor area immediately surrounding the home, is protected. Courts have treated this area as an extension of the house and as such subject to all the privacy protections afforded a person’s home (unlike a person's open fields) under the Fourth Amendment. However, courts have held aerial surveillance of curtilage not to be included in the protections from unwarranted search so long as the airspace above the curtilage is generally accessible by the public.

An area is curtilage if it "harbors the intimate activity associated with the sanctity of a man's home and the privacies of life."  Courts make this determination by examining "whether the area is included within an enclosure surrounding the home, the nature of the uses to which the area is put, and the steps taken by the resident to protect the area from observation by people passing by." Theoretically, many structures might extend the curtilage protection to the areas immediately surrounding them. The courts have gone so far as to treat a tent as a home for Fourth Amendment purposes in the past.  It is possible that the area immediately surrounding a tent (or any structure used as a home) might be considered curtilage.

Despite this broad interpretation, the courts seem willing to find areas to be outside of the curtilage if they are in any way separate from the home (by a fence, great distance, other structures, even certain plants). 

Exigent circumstance

There are also "exigent circumstances" exceptions to the warrant requirement. Exigent circumstances arise when the law enforcement officers have reasonable grounds to believe that there is an immediate need to protect their lives, the lives of others, their property, or that of others, the search is not motivated by an intent to arrest and seize evidence, and there is some reasonable basis, to associate an emergency with the area or place to be searched. 

Motor vehicle

 

The Supreme Court also held that individuals in automobiles have a reduced expectation of privacy, because vehicles generally do not serve as residences or repositories of personal effects. Vehicles may not be randomly stopped and searched; there must be probable cause or reasonable suspicion of criminal activity. Items in "plain view" may be seized; areas that could potentially hide weapons may also be searched. With probable cause, police officers may search any area in the vehicle. However, they may not extend the search to the vehicle's passengers without probable cause to search those passengers or consent from the passenger(s) to search their persons or effects.

 

In Arizona v. Gant, 556 U.S. ___ (2009), the Supreme Court ruled that a law enforcement officer needs a warrant before searching a motor vehicle after an arrest of an occupant of that vehicle, unless at the time of the search the person being arrested is unsecured and within reaching distance of the passenger compartment of the vehicle or police officers have reason to believe that the evidence for the crime for which the person is being arrested will be found in the vehicle. 

Searches incident to a lawful arrest

Another common law rule—that permitting searches incident to an arrest without warrant—has been applied in American law. The rule permitting searches incident to a lawful arrest has a lengthy common law history.  The justification for such a search is to prevent the arrested individual from destroying evidence or using a weapon against the arresting officer. In Trupiano v. United States, 334 U.S. 699 (1948), the Supreme Court held that "a search or seizure without a warrant as an incident to a lawful arrest has always been considered to be a strictly limited right. It grows out of the inherent necessities of the situation at the time of the arrest. But there must be something more in the way of necessity than merely a lawful arrest." In United States v. Rabinowitz, 339 U.S. 56 (1950), the Court reversed its previous ruling, holding that the officers' opportunity to obtain a warrant was not germane to the reasonableness of a search incident to an arrest. The decision suggested that any area within the "immediate control" of the arrestee could be searched, but it did not define the term. In deciding Chimel v. California, 395 U.S. 752(1969), the Supreme Court elucidated its previous decisions. It held that when an arrest is made, it is reasonable for the officer to search the arrestee for weapons and evidence.

 

Similarly, it was held that it is reasonable for the officer to search the area within the arrestee's immediate control, which is the area from which the defendant may gain access to a weapon or evidence. A warrentless search of the room in which the arrest is made is therefore permissible. However, other rooms may not be searched absent a search warrant or other exigent circumstances, as the arrestee would be unlikely to access weapons or evidence in those rooms at the time of arrest.

Border search exception

Searches conducted at the United States border or the equivalent of the border (such as an international airport) may be conducted without a warrant or probable cause subject to the "border-search" exception.^[73] Most border searches may be conducted entirely at random, without any level of suspicion, pursuant to U.S. Customs and Border Protection plenary search authority. However, searches that intrude upon a traveler's personal dignity and privacy interests, such as strip and body cavity searches, must be supported by "reasonable suspicion."^[74] The U.S. Courts of Appeals for the Fourth and Ninth circuits have ruled that information on a traveler's electronic materials, including personal files on a laptop computer, may be searched at random, without suspicion.^[75]

 

Other exceptions

In New Jersey v. T. L. O., 469 U.S. 325 (1985), the Supreme Court ruled that searches in public schools do not require warrants, as long as the searching officers have reasonable grounds for believing that the search will result in the finding of evidence of illegal activity. However, in Safford Unified School District v. Redding, 557 U.S. __ (2009), the Court ruled that school officials violated the Fourth Amendment when they strip searched a 13 year old girl based only on a student claiming to have received drugs from that student. 

Similarly, in Samson v. California, 547 U.S. 843 (2006), the Court ruled that government offices may be searched for evidence of work-related misconduct by government employees on similar grounds. Searches of prison cells are subject to no restraints relating to reasonableness or probable cause or searches undertaken as a condition of parole.

In a memo dated March 14, 2003, an official in the Bush administration stated "... our Office recently concluded that the Fourth Amendment had no application to domestic military operations". The administration believed that any search or surveillance conducted by the National Security Agency of US citizens communicating with foreign nationals abroad was immune to a Fourth Amendment challenge.  To protect the telecommunication carriers cooperating with the US government from legal action, the Congress passed a bill updating the Foreign Intelligence Surveillance Act of 1978 to permit this type of surveillance. 

In August 2008, the Foreign Intelligence Surveillance Court of Review ruled that the President and the Congress had the authority to wiretap international phone calls and intercept e-mail messages without a specific court order. 

The Supreme Court has not ruled on post-9/11 airport security procedures, but the Ninth Circuit ruled in United States. v. Aukai that "airport screening searches, like the one at issue here, are constitutionally reasonable administrative searches because they are conducted as part of a general regulatory scheme in furtherance of an administrative purpose, namely, to prevent the carrying of weapons or explosives aboard aircraft, and thereby to prevent hijackings." 

Computers and privacy

Over the last decade, courts adjudicated whether the government can access evidence of illegal activity stored on digital technology without violating the Fourth Amendment.

Many cases discuss whether incriminating evidence stored by an employee in workplace computers is protected under the reasonable expectation of privacy. In a majority of cases, employees do not have a reasonable expectation of privacy for electronic communications at work. However, one federal court held that employees can assert the attorney-client privilege with respect to certain communications on company laptops. 

On January 30, 2007, the United States Court of Appeals for the Ninth Circuit in United States v. Ziegler, 497 F.3d 890 reversed its earlier August 2006 decision upon a petition for rehearing. In contrast to the earlier decision, the Court acknowledged that an employee has a right to privacy in his workplace computer. The court also found that an employer can consent to searches and seizures that would otherwise be illegal. 

      In Ziegler, an employee had viewed at work websites of child pornography. His employer noticed the conduct, made copies of the hard drive, and gave the FBI the employee's computer. At his criminal trial, Ziegler filed a motion to suppress the evidence on the ground that the government violated the Fourth Amendment rights. The Ninth Circuit allowed the lower court to admit the evidence. After reviewing the relevant Supreme Court opinions on a reasonable expectation of privacy, the court acknowledged that Ziegler had a reasonable expectation of privacy at his office and on his computer. However, the court found that the employer could consent to a government search of the computer without infringing on the Ziegler's Fourth Amendment rights.

On March 11, 2010, the United States Court of Appeals for the Eleventh Circuit ruled, in Rehberg v. Paulk, 598 F.3d 1268, that a person does not have a reasonable expectation of privacy in an e-mail once any copy of the communication is delivered to a third party. 

On December 14, 2010, in United States v. Warshak, the United States Court of Appeals for the Sixth Circuit ruled that a person has a reasonable expectation of privacy in his emails and that the government violated Warshak's Fourth Amendment rights by compelling his internet service provider to turn over his emails without first obtaining a warrant based upon probable cause. 

On January 3, 2011, in The People v. Gregory Diaz, the Supreme Court of California ruled for allowing warrantless search by the police of suspects' cell phones at the time of the arrest, on the grounds of preventing destruction of evidence such as text messages 

the loss of privacy upon arrest extends beyond the arrestee's body to include “personal property... immediately associated with the person of the arrestee” at the time of arrest.  this loss of privacy entitles police not only to “seize” anything of importance they find on the arrestee's body  , but also to open and examine what they find.