In the 1920s, the national Prohibition of alcoholic beverages led to a vast increase in the federal government’s crime-fighting role and in the workload of the federal courts. The Eighteenth Amendment, ratified on January 16, 1919, prohibited the manufacture, transportation, and sale of “intoxicating liquors,” and the amendment granted Congress and the states “concurrent power to enforce this article.” The architects of national Prohibition anticipated that the states would assume the burden of enforcement, but, in practice, much of the responsibility fell on federal officials. Prohibition enforcement required an unprecedented scale of federal policing, which soon produced an overwhelming number of criminal prosecutions in the federal courts. For the thirteen years of national Prohibition (1920–1933), cases arising from the violation of the federal Prohibition laws averaged close to two-thirds of all U.S district court cases. The number of criminal cases handled annually by the federal district courts grew from 54,487 in 1921 to 92,174 in 1932. These criminal trials also prompted appeals in every judicial circuit. By 1925, appeals of criminal convictions in the Ninth Circuit, prompted mostly by Prohibition, constituted nearly 40% of the appeals court’s work.
The increased workload in the federal courts was one of the many unexpected demands placed on the federal government by Prohibition, which redefined the government’s role in the daily lives of citizens. Inadequate federal forces confronted popular disregard or opposition to the ban on liquor, and the nearly impossible task of enforcing major changes in personal behavior threatened to erode popular respect for federal authority and the judicial process. Federal enforcement also relied on new kinds of evidence gathering, such as wiretapping of phones, that prompted additional concerns about the role of the federal government and the costs of national Prohibition. The expansion of federal criminal prosecutions and the methods used by government agents presented the federal courts, including the Supreme Court, with new and difficult constitutional questions regarding entrapment, double jeopardy, property forfeiture, trial by jury, federalism, and, especially, search and seizure.
The case of Roy Olmstead reflected many of the challenges confronting the federal judicial system during national Prohibition. Olmstead ran a large bootlegging operation, importing liquor from Canada and selling it throughout Seattle, Washington. His illegal business was protected by the local police and employed a workforce at least three times the size of the federal unit responsible for enforcing Prohibition in the area. In an effort to establish evidence of Olmstead’s criminal activity, federal officers tapped his phone. The testimony of what the federal officers overheard was central to the prosecution of Olmstead and the members of his gang, who were charged with conspiracy to violate the National Prohibition Act. The Olmstead case raised two important constitutional questions: Did the use of evidence gathered by the wiretap violate the defendants’ rights under the Fourth Amendment? And did the reliance on the wiretapped conversations to prove conspiracy violate the Fifth Amendment’s protection against self-incrimination? The case also raised questions about the use of evidence gathered in violation of Washington state law that prohibited wiretaps. Throughout the Olmstead proceedings, the federal courts confronted the impact of new technology and its effect on traditional legal definitions of privacy and personal liberty. The telephone and the accompanying revolution in communications required the courts to consider the application of the Bill of Rights to conditions unimagined by the framers, and the courts’ decisions about the Fourth and Fifth Amendments directly influenced popular opinion about the continuing experiment in national Prohibition.
National Prohibition and its enforcement
Congress approved the National Prohibition Act, better known as the Volstead Act, on October 18, 1919. Congress assigned the Act’s federal enforcement responsibilities to the Bureau of Internal Revenue, despite the protests of the bureau’s commissioner and the Secretary of the Treasury, who cited the lack of staff and institutional support for adequate enforcement. The Bureau of Internal Revenue created a small police force of Prohibition agents to help the states and other federal officers enforce Prohibition, and by 1921 federal directors of Prohibition enforcement were appointed in each of the forty-eight states. The federal enforcement agents were exempt from civil service regulations, salaries were low, and the resulting force was small, inexperienced, and frequently corrupt. The President’s commission on enforcement in 1931 reported that “a substantial number of Prohibition agents and employees actually were indicted and convicted of various crimes.” The federal agents, however, did arrest many liquor law violators, and the unmanageable number of resulting cases forced U.S. attorneys to rethink how they prosecuted crimes.
At the beginning of national Prohibition there was virtually no coordination between prosecutors and investigators of crimes. U.S. attorneys, who served in each U.S. judicial district, were presidential appointees under the authority of the Justice Department. U.S. attorneys took the cases that other federal officials, such as Prohibition agents, developed for them, and exercised wide latitude in deciding whether to prosecute fully or not. Between 1921 and 1929, Assistant Attorney General Mabel Walker Willebrandt led the Justice Department’s attempt to coordinate the prosecution of Prohibition crimes, and the Justice Department encouraged U.S. attorneys to bring conspiracy charges, which were easier to prove than were charges of liquor law violations.
Prohibition in Seattle: The Olmstead ring
In Seattle, as in many American cities, the lucrative nature of the illegal liquor trade encouraged the expansion of organized criminal gangs. It is unknown when police lieutenant Roy Olmstead first became a bootlegger, but he was arrested for smuggling liquor in March 1920, when national Prohibition was just weeks old. He was fired from the police force. He later pled guilty and paid a $500 fine. From the time of this arrest, Olmstead was a full-time bootlegger. Indeed, he became, as the newspapers called him, King of the Northwest Bootleggers.
Olmstead’s service in the police department taught him the requirements for success as a bootlegger, and the bribes he had accepted as an officer gave him ready funds to invest. He was the chief manager of a gang, coordinating all the details of what became a complex business. Olmstead procured his liquor in the Canadian province of British Columbia. At the start of United States Prohibition, the Canadian government imposed an extra tax on spirits bought for shipment to the United States. Most bootleggers merely paid the tax and passed it on to their customers. Olmstead avoided the tax by presenting forged documents indicating that he was shipping his liquor to Mexico. This willingness to break Canadian law allowed Olmstead to get all the liquor he needed at a price much lower than that paid by his competitors. He loaded his liquor onto an ocean-going vessel sailing to Mexico and then sent the liquor into the United States by smaller boatloads. Once in the United States, the liquor was shipped by truck and stored in various locations, awaiting distribution. To get liquor, customers called Olmstead’s phone and placed orders; cars then delivered the liquor.
The gregarious Olmstead was known to the business and political elite of Seattle, and he found a ready clientele in a market that depended on personal connections. At its peak, Olmstead’s business was delivering over 200 cases of liquor daily to Seattle residents, hotels, and restaurants. The business gave Olmstead the money to buy an expensive house and to establish Seattle’s first radio station. In one year he admitted on his tax return to earning $19,000 or $20,000 more than the previous year. Olmstead bribed the Seattle police and the sheriffs of King County to ignore his operations. His brothers remained on the police force, and one of his former associates became head of the local enforcement unit, so state and local authorities never threatened Olmstead’s business. Olmstead only had to worry about federal law enforcement.
Federal enforcement of Prohibition in Washington State
Federal Prohibition agents were initially appointed by the Commissioner of Internal Revenue and, starting in 1921, by a state enforcement director. Roy C. Lyle, the director for the state of Washington, was a close associate of one of the state’s U.S. senators, but Lyle had no experience in law enforcement. Lyle left much of the day-to-day operations to his legal advisor and chief assistant, William M. Whitney. A Seattle lawyer and Republican politician, Whitney was a vigorous enforcer of the law and authorized the searches of the cars and homes of leading citizens. Within a year of his appointment he was widely attacked in the press for these tactics. Whitney took the lead in pursuing Olmstead and endorsed investigation methods that would raise important constitutional issues in the federal courts. As in other states, many of the agents working under Whitney misused their office when performing undercover operations, and the agents faced allegations of drinking heavily and patronizing prostitutes. Some agents were so notorious that juries refused to convict on their word, and judges rebuked the agents for their actions. The district officers nevertheless enforced the liquor ban through many arrests. By one internal account, the agents in Washington made over 7,000 arrests before 1927.
Wiretapping the bootlegger
Beginning in June 1924, federal Prohibition agents, for months on end and with no authorizing warrants, listened to the phone conversations of Roy Olmstead and other members of his bootlegging gang. Even though the wiretappers were not on the line around the clock, the number of overheard conversations made for over 700 pages of transcripts, many of which were compiled by the wife of William Whitney. But the wiretaps did not generate the evidence that would enable the government to catch gang members in the act of smuggling or selling liquor.
The wiretaps were unproductive in part because Roy Olmstead was aware of them. According to the defendants, the chief wiretapper approached Olmstead and offered to sell him transcripts of his phone conversations. Olmstead refused to buy, convinced that the federal rules of evidence and Washington state law would not allow such evidence to be submitted in court.
Until the Olmstead case, the federal courts had established few rules about wiretap evidence or about the privacy of telephone conversations. In an age when many telephone users had access only to shared “party” lines, many people did not have the same expectations of privacy that would be assumed by later generations. The ability to tap telephone lines, however, like the introduction of technology to intercept telegraph wires in the late nineteenth century, did raise many concerns about protecting confidential communications. Most states had laws to protect telegraph communications, and by 1910 the majority of states had enacted restrictions on the tapping of telephone conversations. Law enforcement officials, however, had used wiretapping in criminal investigations, and federal officials relied on wiretaps during the surveillance of suspected radicals during World War I. Wiretaps became more frequent in federal investigations during Prohibition but no federal statutes or federal case law regulated wiretaps, and many officials were concerned about the use of evidence gained from intercepted conversations. In 1924, under Attorney General Harlan Fiske Stone, the Federal Bureau of Investigation forbade Department of Justice agents from engaging in wiretapping. (By the time Olmstead reached the Supreme Court, Stone was sitting as a justice on the Court.) Olmstead was the most notable of the Prohibition-era cases that brought to the federal courts essential questions about legal status of telephone conversations. Did callers have a right to privacy in their telephone conversations? Were telephone conversations similar to mailed letters, which were protected by the Fourth Amendment?
While the wiretap would create the constitutional issue in the case, it was the actions of the Canadian government that made possible the prosecution of Olmstead. The Canadians caught three of Olmstead’s men with a large boatload of liquor, illegally bound for the United States. The testimony of the Canadians, augmented by the information from the wiretaps, provided Whitney with enough evidence to secure a search warrant and raid on the night of November 17/18, 1924. The records seized that night, supplemented with what the federal agents had learned through the wiretaps and from the testimony of gang members, were used by the U.S. attorney’s office to convince the grand jury to indict Olmstead and ninety others for conspiracy to violate the National Prohibition Act.
From indictment to trial
On January 19, 1925, a federal grand jury, empanelled in the U.S. District Court for the Western District of Washington, charged ninety-one individuals with four different counts of conspiracy to violate federal law. (The crime of conspiracy consists of two or more people agreeing to commit a crime and one member of the group taking some action toward carrying out the plan. All members of the conspiracy are equally liable for the actions of any members, but the prosecution must establish that those involved in the conspiracy intended to break the law.) The indictment charged the individuals with two counts of conspiring to import and to sell prohibited alcoholic beverages in violation of the National Prohibition Act and with two counts of conspiring to defraud the national revenue and to import prohibited merchandise in violation of the Tariff Act of 1922. The indictment listed the individual’s names, some with aliases such as “Shorty,” “Baldy,” and “Brownie.” Among the indicted were two Seattle police officers.
Between the indictment in January 1925 and the trial in January 1926, Olmstead and most of the members of his organization returned to the bootlegging business. Olmstead’s attorney, Jerry L. Finch, himself a codefendant, presented the court with several motions variously intended to stop the trial, to improve the likelihood of acquittal if the defendants came to trial, and to establish grounds for appeal if the defendants were convicted at trial. In a plea to dismiss the indictment, Finch alleged that agent Whitney threatened the foreman of the grand jury and presented the grand jury with insufficient and hearsay evidence. In a second motion, Finch challenged the conspiracy indictment as too vague and too imprecise for the defendants to prepare their case. In separate decisions in April and May of 1925, Judge Jeremiah Neterer of the U.S. District Court for the Western District of Washington rejected these pretrial motions.
Finch and Olmstead filed motions asking the district court to quash the warrants for searches of their offices and Olmstead’s residence, and to exclude the evidence resulting from the searches. In the motions to quash, the defendants argued that the seized records and the wiretap evidence were obtained in violation of the Fourth Amendment’s protections against unreasonable search and seizure, and therefore should be excluded from the trial. The motions also argued that the evidence compromised the defendants’ Fifth Amendment right against self-incrimination, and the defendants asked the judge to order the return of the records to their owners. In September 1925, Judge Neterer rejected the Fourth Amendment arguments and upheld the use of wiretap evidence, but he did specify that the papers seized from Finch and Olmstead could not be used against them in the trial. This, however, was a hollow victory for the defense because those materials could be used against all of the other defendants and, therefore, would not be returned. This ruling made clear the strategic advantage of charging the members of the Olmstead ring with conspiracy, as each could be held liable for the actions of the other members of the conspiracy and evidence that would be suppressed in a trial of a single defendant charged with a crime would be admitted in a conspiracy case.
The prosecution, headed by U.S. Attorney Thomas Revelle and assisted by Charles T. McKinney and John Marshall, worked with William Whitney to prepare the evidence for trial. The prosecution convinced members of the Olmstead organization to testify for the prosecution. One member of the organization, Alfred Hubbard, asked for and received an appointment as a federal Prohibition agent in exchange for inside information. Hubbard was the probable source that allowed federal agents to catch Roy Olmstead on Thanksgiving morning 1925, unloading liquor from a boat.
By the opening of the trial on conspiracy charges, twelve defendants had pleaded guilty and agreed to testify against the others. Another twelve defendants hired the combative George Francis Vanderveer to defend them; others hired their own lawyers. And another thirty-two defendants fled to Canada, forfeiting their bail. Only forty-seven individuals, including Roy Olmstead and Jerry Finch, remained to stand trial in Seattle beginning on January 19, 1926. At the opening of the trial, the government attorneys decided not to prosecute the two charges related to the Tariff Act. The jury was selected in two days and was sequestered for the duration of the trial.
The prosecution detailed the Olmstead ring operations, from the procurement of the liquor to its final distribution. Witnesses described the acquisition of boats, trucks, and property to facilitate the trade. Prominent Seattle citizens, most notably the business magnate William E. Boeing, testified about the purchase of liquor through the phone order service provided by the Olmstead gang. The testimonies of members of the gang who pleaded guilty and the federal agents who had listened in on the telephone taps were central to the prosecution’s case. While the transcripts of the tapped conversations were never entered into evidence, the federal agents who had listened into the conversations were allowed to use the transcripts to refresh their memories when testifying. These witnesses described the full range of the smuggling and sale of liquor as well as the corruption of the local police.
The defense attempted to discredit or to exclude the wiretapped evidence. Vanderveer successfully challenged the identification of speakers on some of the wiretaps, and the government consequently dismissed indictments against thirteen people. By the end of the trial in February 1926, charges against five more defendants were dismissed, leaving only twenty-nine defendants. The jury deliberated for six hours over two days and found twenty-one of those defendants guilty. Among those convicted were Roy Olmstead and Jerry Finch.
Before the sentencing in March, Judge Neterer carefully reviewed the records of those convicted and levied heavier sentences on those who were repeat offenders or whom the evidence showed were the leaders of the ring. Olmstead received the heaviest penalties: four years in prison and $8,000 in fines. In sentencing him, Neterer said: “The operation of this conspiracy, as disclosed by the testimony was scandalous and of incalculable damage to society and the organization of government. . . . If the same energy and organization had been directed along legitimate lines . . . great good might have obtained.” Jerry Finch was sentenced to two years and fined $500. Finch received the lowest fine, while the least prison time ordered by Judge Neterer was eighteen months. At the same time, Neterer rejected all the defense motions for arrest of judgment, saying, “I think all the points raised were ruled upon during the trial . . . the defendants were given every legal right.”
After the sentencing, the great majority of the defendants, upon payment of their bails, were free while their lawyers planned their appeals. Before the U.S. Circuit Court of Appeals for the Ninth Circuit, Finch and Vanderveer, in appeals for separate groups of defendants, repeated their trial court arguments that the tapping of the phone lines constituted an illegal search in violation of the Fourth Amendment and that the introduction of the wiretapped evidence in court violated the defendants’ Fifth Amendment rights against self-incrimination. On May 9, 1927, Judge William Ball Gilbert, joined by Judge Frank Dietrich, ruled that “the purpose of the amendments is to prevent the invasion of homes and offices and the seizure of incriminating evidence found therein.” He did not see wiretapping as such an invasion, equating it with “evidence obtained by listening at doors or windows.” The court’s majority also denied the appellants’ claim that the grand jury had been coerced to return the indictment and the claim that the witnesses had improperly relied on transcripts of the wiretapped conversations.
In his dissenting opinion, Judge Frank Rudkin found that the witnesses had improperly relied on the transcripts, and concluded that “a better opportunity to color or fabricate testimony could not well be devised by the wit of man.” Rudkin, however, quickly added that his dissent was based on “much broader grounds.” The testimony drawn from the wiretaps was inadmissible in “any event” because it so clearly violated the protections offered by the Fourth and Fifth Amendments. The amendments’ “chief aim and purpose was not the protection of property, but the protection of the individual in his liberty and in the privacies of life.” He noted “a growing tendency to encroach upon and ignore constitutional rights,” but pointed out that the Supreme Court had “consistently and persistently declared that the amendments in question must be liberally construed in favor of the citizen and his liberties, and that stealthy encroachments will not be tolerated.”
Lawyers for Olmstead and two other groups of defendants submitted petitions appealing the case to the Supreme Court of the United States. In the fall of 1927, Olmstead was tried and acquitted on separate federal charges arising from his arrest on Thanksgiving Day 1925. Without wiretap evidence, and relying on the dubious testimony of Alfred Hubbard, the U.S. attorney was unable to convince a jury to convict Olmstead. Five days after this acquittal, the Supreme Court denied the petitions for certiorari. Within a week, Olmstead, Finch, and others entered federal prison.
After two groups of appellants applied for a rehearing of their petitions, the Supreme Court reconsidered and, on January 9, 1928, agreed to hear arguments in the Olmstead appeal and two companion cases (Green v. United States and McInnis v. United States). The Supreme Court limited arguments in the combined cases to the Fourth and Fifth Amendment questions raised by the reliance on evidence gathered by wiretapping.
Prohibition in the Supreme Court
In a series of cases in the 1920s, the Supreme Court had almost always supported the enforcement of Prohibition, although the demands of federal policing and the social reform goals of the liquor ban often produced unpredictable voting alliances on the Court. The Chief Justice of the United States was William Howard Taft, the former President, appointed to the Supreme Court in 1921. Taft, who served as a professor at Yale Law School before joining the Court, had originally opposed Prohibition, in part because of the unsustainable burden it would place on the federal court system. But once the Eighteenth Amendment was ratified and he joined the Supreme Court, Taft was determined to support the enforcement of democratically enacted and constitutionally authorized federal law. Other conservative justices on the Supreme Court, such as George Sutherland and James McReynolds, distrusted the social engineering goals of Prohibition and feared that strict enforcement would undermine public confidence in the federal courts. Justices like Louis Brandeis and Oliver Wendell Holmes generally supported the enforcement of laws passed by the Congress, but they became increasingly concerned about the lack of public support for strict enforcement of Prohibition and also questioned the police’s enforcement methods.
Mabel Walker Willebrandt, who usually represented the government before the Supreme Court in Prohibition-related cases, travelled to Seattle to observe the trial, and although she signed the government’s brief asking the Supreme Court not to grant certiorari, she refused to represent the government at oral arguments in Olmstead because she opposed the use of wiretap evidence. The Supreme Court heard arguments in Olmstead and the related cases on February 20 and 21, 1928; on June 4 of that year, the Court announced its decision in the case. In a five-to-four decision, the Court, in an opinion written by Chief Justice Taft, affirmed the decisions of the U.S. court of appeals and thus upheld the convictions. The Supreme Court held that the wiretaps entailed no entry into Olmstead’s home or office and thus the wiretap evidence was not obtained through violations of the search and seizure limitations of the Fourth Amendment. In addition, Taft declared that phone conversations were not the equivalent of sealed letters, which previous Supreme Court decisions had protected from warrantless searches and seizures. Taft held that the invention of the telephone had not changed the meaning of the Fourth Amendment. “The language of the Amendment can not be extended and expanded to include telephone wires reaching to the whole world from the defendant’s house or office. The intervening wires are not part of his house or office any more than are the highways along which they are stretched.” Taft added that Congress was free to protect telephone communication through legislation, but the courts could not do so without distorting the meaning of the Fourth Amendment.
There were strong dissents from Justices Pierce Butler, Oliver Wendell Holmes, and Louis Brandeis; Justice Harlan Fiske Stone concurred with most of the dissents. Justice Butler saw a clear analogy between private telephone conversations and letters, and therefore concluded that the Fourth Amendment limitations on searches and seizures should apply in the case. “The contracts between telephone companies and users contemplate the private use of the facilities employed in the service. The communications belong to the parties between whom they pass.” Justice Holmes asserted that as a matter of policy and principle the government should not allow the introduction of evidence obtained in violation of Washington state law, for “if the Government becomes a lawbreaker, it breeds contempt for law.”
In the lengthiest and most noted dissent, Justice Brandeis asserted a general “right to be let alone” from government intrusion and argued that the purpose of the Fourth Amendment was to secure that right. In contrast to Taft and the Court’s majority, Brandeis found that “there is, in essence, no difference between the sealed letter and the private telephone message.” The protections of the Fourth Amendment, he said, did not apply solely to the medium familiar to the framers of the Constitution. “Time and again, this Court in giving effect to the principle underlying the Fourth Amendment, has refused to place an unduly literal construction upon it.” Having found a violation of the Fourth Amendment, Brandeis concluded that the use of the wiretap evidence had violated the defendants’ Fifth Amendment protection against self-incrimination. Brandeis added that he would have reversed the lower court decisions regardless of the constitutional questions because of the admission of evidence that had been obtained in violation of Washington state law prohibiting wiretaps. In his opinion for the majority, Taft dismissed this objection, stating that the common law had long permitted the use of illegally or improperly obtained evidence.
Much of the public reaction to the Supreme Court’s decision in Olmstead was critical. A popular magazine, The Outlook, went so far as to label Olmstead the “the Dred Scott decision of Prohibition.” The comparison to the Supreme Court’s most reviled decision may have been exaggerated, but it reflected the growing concern that the enforcement of national Prohibition was damaging public confidence in the federal court system and undermining public respect for law enforcement. Before he became Chief Justice and before the ratification of the Eighteenth Amendment, William Howard Taft had warned that national Prohibition would be “an irretrievable national blunder” that would be unenforceable and a threat to the proper balance of state and federal governmental responsibilities. Following Taft’s decision in Olmstead, more and more commentators concluded that Prohibition had become a threat to the rule of law in the United States. According to The Nation, the Court had endorsed a kind of “lawlessness” in a misguided effort to enforce Prohibition. The Court’s acquiescence in what a leading business newspaper called the “dirty business” of wiretapping came to symbolize a level of federal intrusion that many were not willing to accept. Even a leader of the Anti-Saloon League protested the acceptance of wiretapping, which he feared would turn public opinion against Prohibition.
The reaction to Olmstead reflected growing disenchantment with Prohibition and doubts about the possibilities of effective enforcement. Although Herbert Hoover had supported the continuation of Prohibition in his successful presidential campaign in 1928, both political parties were seriously divided over the issue. After 1928, a growing number of studies documented the law enforcement challenges and judicial burdens of Prohibition. In 1928 and 1929, nearly two-thirds of the criminal cases in federal courts were related to Prohibition, and in 1930 federal prisons housed twice the number of prisoners they could normally accommodate. In May 1929, President Hoover appointed a commission to study “Law Observance and Enforcement.” The commission, in its report released in January 1931, recommended efforts to enforce the Eighteenth Amendment, but its findings indicated how difficult that would be. The report documented increased consumption of alcohol, a rise in criminal activity associated with the manufacture and sale of alcoholic beverages, and the crushing burden on law enforcement forces and the nation’s courts.
Organizations supporting the repeal of the Eighteenth Amendment, including the Women’s Organization for National Prohibition Reform, established by socially prominent women from throughout the nation, began to coordinate their campaign for repeal. The Democratic Party platform of 1932 endorsed repeal, and although both parties remained divided over the issue, the overwhelming victory of the Democrats in November 1932 was interpreted by most as a referendum in favor of repeal. The new Congress, on February 20, 1933, approved a constitutional amendment repealing the Eighteenth Amendment, and Congress provided for popularly elected state conventions to consider ratification. A majority of Republicans as well as Democrats in Congress approved the amendment. On December 5, 1933, the Twenty-First Amendment was ratified when Utah’s state convention became the thirty-sixth convention to approve it.
In the spring of 1931, Roy Olmstead was released from prison a changed man. He had become a Christian Scientist and had renounced liquor. The repeal of Prohibition strengthened support for pardons of many convicted of violating the Volstead Act, and on Christmas 1935, Olmstead received a full presidential pardon and remittance of fines paid. In 1934, Congress passed a communication act that would in just a few years serve as the basis for Supreme Court decisions prohibiting wiretapping by federal agents without a warrant.