The Fourth Amendment prohibits unreasonable searches and seizures, generally requiring that law enforcement obtain a warrant from a neutral and detached magistrate upon a showing of probable cause. In 1928, the Supreme Court determined in Olmstead v. United States that projected voices passing over telephone wires beyond a person's home were not protected by the Fourth Amendment, so no warrant was required for a wiretap installed outside of the home. Since the Olmstead decision, the case law and statutory framework governing law enforcement surveillance of real-time communications has changed significantly. This In Focus provides a brief history of the Fourth Amendment's application to such surveillance, an overview of the federal Wiretap Act, selected caselaw interpreting the statute, and considerations for Congress.
In Olmstead, the Supreme Court determined the projection of voices outside the home by telephone to be outside the scope of the Fourth Amendment protections because the Court perceived the text of the Amendment to be focused on "material things—the person, the house, his papers or his effects." By the 1967 case Berger v. New York, the Court's views had shifted. The Court held that a state statute—which permitted a related type of surveillance, eavesdropping, when authorized by a court order—was unconstitutional under the Fourth Amendment. Explaining its concern about the development of "sophisticated electronic devices," which "pick up whispers in a room," the Court identified several aspects of the statute that did not "carefully circumscribe[]" the circumstances under which courts could authorize electronic eavesdropping to prevent so-called "general searches" through electronic listening devices. The Court held that the statute lacked the particularity required by the Fourth Amendment in that it did not require the applicant to describe a particular offense, particularly describe the property to be seized (i.e., the conversations sought), provide notice to parties, or obtain supervision from the court over the execution of the warrant. The decision also condemned the statute's unrestricted, two-month authorization and lack of sufficient probable cause for extensions. Later in 1967, in Katz v. United States, the Court clarified that the Fourth Amendment applies to "people, not places," officially overturning Olmstead's physicality requirement and setting a threshold "reasonable expectation of privacy" test for Fourth Amendment queries.
Following Olmstead, in 1934, Congress enacted a federal law prohibiting the interception of communications over wires, including by federal law enforcement as evidence in criminal proceedings. In 1968, after the Berger and Katz decisions, Congress enacted Title III of the Omnibus Crime Control and Safe Streets Act of 1968 (Title III or the Wiretap Act) with the dual purpose of "properly protect[ing] the privacy of oral and wire communications, while providing a uniform basis for authorizing their interception in appropriate cases."
Title III, as amended, generally prohibits the interception of wire, oral, and electronic communications (including wiretapping and eavesdropping). The categories of information cover aural transfers of the human voice using wires, cables or like connections (such as telephones), communications between two people with an expectation of privacy, and transfers of signs, signals, writing and other data, such as emails and text messages. Courts have generally found the statute to apply to the real-time, contemporaneous interception of communications, not to prior recordings. There are numerous exceptions to Title III's coverage, including for certain types of electronic communications, intelligence interceptions and technical assistance, and certain interceptions when one of the parties to the communication consents.
In 18 U.S.C. § 2518, the statute sets forth detailed procedures for federal law enforcement to obtain court-ordered interceptions of communications and authorizes certain state interceptions in conformity with that section. The statute also permits emergency interception in specific situations, usually involving an imminent threat to life, while requiring a full application to a court within 48 hours of interception.
Under 18 U.S.C. § 2516, only a specifically designated Deputy Assistant Attorney General or higher official at the Department of Justice (DOJ) may authorize an application for a federal wiretap of wire or oral communications. In contrast, any attorney for the government, as defined by the Federal Rules of Criminal Procedure, may authorize an application for electronic communications. Reviewing § 2516, in United States v. Giordano, the Supreme Court stated that "[t]he mature judgment of a particular, responsible Department of Justice official is interposed as a critical precondition to any judicial order" and suppressed evidence obtained through an application signed by the Attorney General's executive assistant.
Relying on Giordano, the Second Circuit determined that a similar requirement that the interception order be authorized only from a "court of competent jurisdiction" precludes a federal judge's delegation of authority to a magistrate judge.
To issue an interception order under Title III, a judge must find probable cause that "particular communications" about an enumerated offense will be obtained through interception of the facility (usually a phone, device) or target location. The law enforcement officer's affidavit must generally establish probable cause to believe that the suspects are using the targeted facility to conduct the criminal activity. DOJ has historically imposed strict time constraints on such probable cause evidence to avoid staleness challenges.
Federal application packages for Title III authorization typically comprise an application, affidavit, and draft order. Each application for an interception requires the identification of the applicant and a sworn "full and complete statement of the facts and circumstances relied upon by the applicant, to justify his belief that an order should be issued." This statement must identify the suspects, the target facilities or locations, and the criminal offenses under investigation. The application package must describe the facility to be intercepted with particularity; however, upon a showing that targets are evading law enforcement's detection, the statute authorizes a roving wiretap tied to a person in lieu of a facility under certain conditions. Reviewing courts have generally distinguished between roving wiretaps and wiretap authorizations for cell phones (including those encompassing changing cell phone numbers associated with a listed serial number or other identifier).
The law enforcement application package must include a "full and complete" statement of investigative techniques that have been "tried and failed or why they reasonably appear to be unlikely to succeed if tried or to be too dangerous" to "assure that wiretapping is not resorted to in situations where traditional investigative techniques would suffice to expose the crime." Such traditional techniques typically include surveillance, interviews, infiltration, search warrants, and review of call records. Although the application's description of such techniques must avoid generalities and conclusory statements and "specifically relate to the individuals targeted by the wiretap," courts have found that this requirement is not "designed to force the government to exhaust all other conceivable investigative procedures."
Interception must be conducted "in such a way as to minimize the interception of communications not otherwise subject to interception." In Scott v. United States, the Supreme Court explained that this provision does "not forbid the interception of all nonrelevant conversations" but requires law enforcement's minimization to be reasonable based on the facts and circumstances of each case. In determining the reasonableness of the minimization, lower courts have looked at the factors identified in Scott, such as the percentage of non-pertinent calls intercepted, the length of calls, the use of code language, the extent of the conspiracy, and the stage of the investigation.
The application package typically includes a minimization plan, which can rely on civilian monitors if supervised by an investigative or law enforcement officer and noticed to the court. Minimization is conducted in real time with the exception of communications in a foreign language or code, which must be minimized as soon as practicable.
Addressing the concerns of the Berger Court as to the extent and length of eavesdropping and wiretapping orders, 18 U.S.C. § 2518(5) limits the duration to not "longer than is necessary to achieve the objective of the authorization, nor in any event longer than thirty days," with strict requirements for extensions.
Notice to the intercepted parties after the fact is required, as are protections for intercepted communications and applications. Individuals in violation of the provisions of Title III are subject to potential criminal and civil liability.
The statute contains annual reporting requirements for state and federal judges issuing wiretap orders. In 2025, judges reported a total of 1,735 state and federal wiretaps authorized. Drug offenses were the most prevalent type of offense identified, and the average cost was $92,963 per wiretap.
18 U.S.C. § 2518(10)(a) provides for suppression of wire and oral communications evidence if (i) the interception was unlawful, (ii) the order was insufficient on its face, or (iii) the interception was not made in conformity with the order of authorization or approval. In Giordano, the Supreme Court found that the statute required suppression for an unauthorized delegation because the authorization provision "play[s] a central role in the statutory scheme." After Giordano, courts concluded that "not every failure to comply fully with . . . Title III necessitates suppression." To determine whether suppression was mandatory, courts generally have focused on whether the transgressed statutory provision played a central or substantive role in the regulatory system established by Congress.
In 2018, the Supreme Court clarified that § 2518(10)(a)(i) applies when the "Government's use of a wiretap is unconstitutional or violates a statutory provision that reflects Congress' core concerns." Subparagraph (ii) applies when the order lacks information required by the statute; and subparagraph (iii) applies when the "Government fails to comply with conditions set forth" in the authorization.
Both Title III and the Giordano decision predate the judicially created exception to the exclusionary rule, which can preserve evidence if the government acted in good faith. Federal appeals courts have disagreed whether the doctrine can be applied to avoid suppression of wiretap evidence or whether the statute requires suppression, irrespective of a showing of good faith.
The Supreme Court has interpreted the Fourth Amendment to establish discrete parameters around law enforcement's interception of real-time communications. Through Title III, Congress codified the Court's standards and provided uniform guidance to law enforcement and courts to enable criminal investigations and prosecutions. Congress has amended the statute through the Antiterrorism and Effective Death Penalty Act, the Communications Assistance for Law Enforcement Act, and the Electronic Communications Privacy Act, among others, to encompass new technology and to facilitate law enforcement access to these investigative tools. Congress may continue to examine these provisions in the face of emerging technology and caselaw and legislate, if it chooses to, in line with the Court's Fourth Amendment jurisprudence.