The Fourth Amendment was created in 1791 primarily to end the existence of general warrants, which the American colonialists hated and feared. These warrants were used by the English government to conduct door-to-door searches and mass arrests, often as a coercive method for achieving social and political goals (Maclin and Mirabella, 2011, p. 1052). With this history in mind the text of the Fourth Amendment makes perfect sense:
"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." (FindLaw, 2011)
The wording of the Fourth Amendment represents a straightforward attempt to eliminate general warrants and thus protect personal privacy, which no one really argues with, but other concepts within the text have been the source of much debate ever since it was written. The phrase "probable cause" is not well defined, either in the Amendment or the historical documents created around the time the Constitution was written (Maclin and Mirabella, 2011, p. 1057-1059). Depending on the judge or magistrate in charge of a hearing taking place during the early days of the republic, "probable cause" could have been defined somewhere between "likely" and "credible." Today the meaning of "probable cause" is modified by the concept of reasonableness, which is defined both by public norms and the level of interest the state has in conducting a search and seizure (Ohm, 2010, p. 1517).
There are even some today who would prefer to interpret the Fourth Amendment literally, in the absence of historical context (Maclin and Mirabella, 2011, p. 1061). Although this may seem reasonable on the surface, such an interpretation would imply that the police are not required to obtain a warrant prior to conducting a search and seizure if a test of reasonableness can be met. The danger in taking this approach is that it transfers authority for granting searches and seizures from the judiciary to the police officers patrolling the streets. Without a check against arbitrary intrusions that a judicial warrant provides, general warrants would likely reemerge as a method for harassing and intimidating segments of the population. Some would argue that has already happened in a post-9/11 America (Totenberg, 2011, para. 9).
Fourth Amendment Interpretations Prior to September 11, 2001
In 1886 the U.S. Supreme Court held in Boyd v. United States that it is not the manner of state intrusion into personal lives that matters, but that the invasion occurred at all (Mell, 2002, p. 382-384). The Court emphasized that the expectation of privacy was not limited to a person's home, but also encompassed all aspects of their lives. This decision was overturned in part in 1928 when the Court considered Olmstead v. United States and found that wiretaps capture nothing physical or tangible and therefore cannot be a search or seizure under the Fourth Amendment. The 'physical' requirement survived until 1967, at which time the Court reverted to its 1886 stance by holding in Katz v. United States that a person having a phone conversation in a public phone booth had a "reasonable" expectation of privacy (Mell, 2002, p. 386-388).
Obtaining a warrant in advance was also emphasized by the Court in Katz, which held that "antecedent justification" is required for engaging in a search (Mell, 2002, p. 386-388). The only exceptions to the antecedent justification requirement that have been recognized by the Court over the years are searches incident to an arrest, stop and frisk searches, automobile searches, searches at port of entries, and searches of closed containers in automobiles that have been lawfully stopped.
Modern interpretations of the Fourth Amendment have become increasingly important as advances in technology provide multiple avenues of 'non-physical' intrusions into personal lives. In Kyllo v. United States the Supreme Court held that technology which enhances human senses, such as thermal imaging, crosses the line from public to private because a person walking down the street would not be able to notice differences in the temperature of a building's roof (Mell, 2002, p. 389-392). In contrast, the Court upheld the lower court finding in California v. Ciraolo that aerial surveillance or photography does not fall under Fourth Amendment protection.
Post-9/11 Fourth Amendment Interpretations
This history of careful and increasingly complex Fourth Amendment jurisprudence was effectively derailed by the passage of the U.S.A. PATRIOT Act (Patriot Act or Act) on October 26, 2001, just 46 days after the tragic events of September 11, 2001 (9/11). The Act was designed to give the executive branch additional tools with which to fight the threat of terrorism. The hastiness with which the Act was made into law frightened members of Congress enough that they wrote 4-year sunsets into 16 of the more controversial provisions (Herman, 2006, p. 67). In the 10 years since the Patriot Act was enacted the sunsets have failed to eliminate a single provision (Johnson, 2011), despite a significant groundswell of public support for eliminating many of the provisions or the Act itself (Bill of Rights Defense Committee, 2007).
Probably one of the more controversial changes to occur with passage of the Patriot Act is the relaxing of certification and justification requirements for National Security Letters (NSLs; Mell, 2002, p. 393-396). NSLs were originally intended to be used in urgent foreign counter-intelligence cases when time was of the essence. Justification for issuing an NSL depended on the ability to articulate specific facts, and certification required personal authorization by the Director or Assistant Deputy Director of the FBI (Garlinger, 2009, p. 1110-1111). Under the Patriot Act NSLs can now be certified by a field agent, justified by mere 'relevance', and utilized for an expanded number of situations domestically.
The relaxing of NSL criteria may increase the possibility that general warrants will reemerge. For example, between 2003 and 2006 the FBI issued 192,500 NSLs (Dilanian, 2011, para. 20), considerably more than the few thousand per year issued prior to 9/11. After the Inspector General revealed how prevalent their use had become and that more than a few were issued fraudulently, the number used per year dropped dramatically to 14,788 for 6,114 people in 2009 (Yost, 2011, para. 3). Unfortunately, the downward trend reversed last year and 24,287 NSLs were issued for 14,212 people.
NSLs are used by the FBI to gather information from third parties, information which isn't protected by the Fourth Amendment because it was voluntarily provided to third parties (Garlinger, 2009, p. 1112-1113). A number of different federal statutes protected this information from unauthorized access (Mell, 2002, p. 393-394), but the Patriot Act contained provisions that relaxed or eliminated these protections. The information being collected includes bank statements, telecommunication records, credit reports, school records, and any and all information held by internet providers and online third parties. Bringing the information from all these disparate sources together in one place allows the intelligence or law enforcement agency to create revealing dossiers on private citizens. The FBI's Investigative Data Warehouse contains over 1.5 billion records, including information collected through more than 300,000 NSLs (Murray and Crockford, 2011, para. 16).
NSLs, as defined by the Patriot Act, are representative of the way in which the Patriot Act treats private information. Other examples include sections 203b and 203d, which allow for sharing of all information related to criminal investigations with intelligence and other government agencies. Critics of these provisions argue massive personal information databases will be created that include information about citizens not under investigation (Abramson and Godoy, 2006). The same fear surrounds roving wiretaps authorized under Section 206, which allows eavesdropping on any and all devices used by a suspect for communications. Section 215 authorizes access by government agencies to business records, which according to critics can include what books have been purchased from a bookstore or checked out from a library. The scope for sneak-n-peak searches, where the suspect is notified later that they were searched to avoid risking the destruction of evidence or undermining an ongoing investigation, has been expanded under Section 213 to include not only terrorism and foreign intelligence investigations, but also any and all criminal investigations, and without a demonstrable need to delay notification.
The Fourth Amendment was penned to end the practice of general warrants, which were used by the state to arbitrarily search, harass, and intimidate individuals and groups. The solution the Framers came up with was requiring specific warrants to be obtained before a search and seizure can be conducted, a probable cause justification, and a shift in the authority to issue such warrants from the police and military to judges and magistrates. Although the Supreme Court has struggled with defining probable cause, the other core principles of the Fourth Amendment, privacy protection, antecedent justification, and judicial oversight, have been reaffirmed repeatedly over the past 220 years.