After playing an active role in reelecting Truman in 1948, Clark made clear to the White House that he was planning to return to Texas and the practice of law. Following the sudden death of
Supreme court associate justice Frank Murphy, however, Truman nominated Clark to fill the vacancy, partly to bolster the majority of
Chief Justice Fred Vinson, a former cabinet colleague and friend of Clark who, since his appointment three years earlier, had failed to unify the Court. Numerous attacks from across the political spectrum were leveled at the nomination, including charges of "
cronyism," a lack of judicial experience, and objections based in part on his work at the center of Truman's anti-communist agenda and, specifically, the Attorney General's List of Subversive Organizations. Former Roosevelt cabinet members Henry Wallace and
Harold Ickes also leveled broadsides for personal and ideological reasons. Ickes said about the nomination, "President Truman has not 'elevated' Tom C. Clark to the Supreme Court, he has degraded the Court."
The New York Times called Clark "a personal and political friend [of Truman's] with no judicial experience and few demonstrated qualifications." The Clark confirmation hearing before the
Senate Judiciary Committee took place in August 1949. Clark declined to testify in person, stating that he "didn't think that a person who had been nominated to the Supreme Court should testify, [since] it jeopardized his future effectiveness on the Court, [and] that he would invariably testify to something that would plague him." Nonetheless, on August 12, the committee voted 9–2 to send the nomination to the full
Senate with a favorable recommendation. and took the
judicial oath of office on August 24, 1949. and helped provide him with a reliable majority. However, the Court as a whole remained fragmented. In 1953, Vinson died of a heart attack. For the remainder of his tenure on the Court, Clark served alongside Chief Justice
Earl Warren, producing a mix of opinions that makes it difficult to characterize him as either conservative or liberal. Clark backed decisions supporting government enforcement of laws designed to promote racial equality. To this end, he authored or played a critical supporting role in many of the Court's landmark decisions in this area. Several rulings by the Vinson Court, most notably
Sweatt v. Painter and
McLaurin v. Oklahoma State Regents (1950), which held that black graduate students must be allowed into "white" state universities and law schools because the separate black school could not provide an education of equal quality, helped lay the groundwork for holdings including
Brown v. Board of Education (1954). Clark played a critical behind-the-scenes role in
Sweatt and
McLaurin that shaped the discussion and provided a workable solution on this issue, helping to "move the Court from considering equality only as a measurable mathematical construct … to what would become known as intangibles." Clark's role as one of two southern justices gave him additional impact in those cases, such as
Hernandez v. Texas (1954), in which the Court ruled that excluding persons of Mexican ancestry from juries violated the Constitution. He also authored several important decisions on race in the 1960s during the height of the Civil Rights era, including
Anderson v. Martin (1964), which held unconstitutional a Louisiana statute because it required the races of those running for office to be printed on a ballot,
Burton v. Wilmington Parking Authority, which upheld the concept of state action to find that a private restaurant violated the 14th Amendment's Equal Protection Clause, and
Heart of Atlanta Motel v. United States and
Katzenbach v. McClung, which upheld the public accommodations provision of the 1964 Civil Rights Act. Clark also faced many cases addressing the constitutionality of Cold War-era laws that required individuals to affirm that they were not members of particular groups or parties. In this area, Clark generally took a traditionally conservative position to support such requirements, consistent with his work as attorney general. During his first years on the Court, Clark recused himself from many of these cases because they had grown out of challenges to policies and laws Clark had helped initiate or implement. In those cases in which he did participate he generally was deferential to the government, and helped provide the Court with a majority affirming the constitutionality of many such laws.
Garner v. Board of Public Works (1951) was a 5–4 decision he authored that upheld the right of a city to require its employees to file affidavits that they were not, nor had ever been, members of the Communist Party and to take loyalty oaths to that effect. "Past conduct may well relate to present fitness. Past loyalty may have a reasonable relationship to present and future trust," he wrote. But Clark also demonstrated a willingness to strike down such laws when they were excessive or overly broad in their application, specifically when they involved the question of whether an individual knew of the organization with which they were allegedly affiliated. Thus, in
Wieman v. Updegraff (1952), Clark struck down a loyalty statute from Oklahoma that required all state employees to take an oath that they were not and had never been for the past five years members of any organization that had been on the attorney general's list of subversive organizations. "Membership may be innocent," Clark wrote. in the
Oval Office at the
White House. Over the next decade, the shifting Court makeup and the evolution of public sentiment led the Court to find a number of these Cold War statutes unconstitutional. In many instances, Clark was the lone dissenter. Among the most memorable was his solo dissent in
Jencks v. United States, in which he labeled the Court's action a "big mistake," and suggested that allowing an individual charged with falsely swearing that he was not a member of the Communist Party to see reports made by two FBI witnesses against him, "afforded him a Roman holiday for rummaging through confidential information as well as vital national secrets." Clark's dissent sparked congressional legislation overriding the Court's decision and placing limits on the kinds of documents criminal defendants can request. Even as he would demonstrate more progressive views in other areas of the law, Clark continued to exhibit his belief in the government's power to prevent people with certain associations from holding certain jobs. Thus, as late as 1967, he dissented in
Keyishian v. Board of Regents, in which the Court struck down as unconstitutionally vague a law preventing a state university from hiring "subversives." Clark's background as a former prosecutor and attorney general also influenced his views in the area of criminal procedure and cases involving the rights of criminal defendants, often leading him to support the government's prosecutorial efforts, particularly during his early years on the bench. In
Crooker v. California (1958), for instance, he wrote the Court's 5–4 opinion upholding a murder conviction of a man who was repeatedly refused legal counsel and had not been informed of his right to remain silent during fourteen hours between his arrest and confession because, in Clark's view, the police tactics were reasonable and the confession voluntary. Six years later, however, he joined with his more liberal brethren in the landmark decision
Gideon v. Wainwright (1963) upholding the right to a fair trial and due process under the Sixth Amendment and holding that an individual defendant must have an attorney appointed for him if he cannot afford one. Clark dissented in
Miranda v. Arizona, the historic ruling in which the Court held that the Constitution ensures a "right to remain silent." Still, he later clarified that he agreed with the underlying idea of limits on custodial interrogation. Clark also authored the Court's landmark decision in
Mapp v. Ohio, which broadened the Fourth Amendment's prohibition on the prosecution's use of improperly seized evidence, known as the exclusionary rule, to include state prosecutions. Clark's law enforcement background led him to support this approach because he believed that having a
district attorney and a federal prosecutor operating under the same system would ensure that police would be more disciplined and that it would lower the risk of evidence being disallowed. Clark demonstrated this progressive understanding right up through his final day on the bench, writing
Berger v. New York (1967), an important Fourth Amendment decision in which the Court held unconstitutional a state statute allowing electronic eavesdropping. It was a holding that was quite distant from policies he had imposed as attorney general. in 1967 after retiring from the Supreme Court.|alt= Clark also wrote the decision for the Warren Court in a major religion case involving the First Amendment's Establishment Clause and reinforcing the principle of separation of church and state. Clark's opinion in
Abington School District v. Schempp (1963), holding that Bible reading exercises and mandated
prayer in public schools violated the Constitution, offered the most basic and textual type of constitutional interpretation, "The Constitution says that the government shall take no part in the establishment of religion … No means no," he wrote. Clark's work as a Supreme Court justice generally is viewed favorably by legal historians. As one scholar noted, he was "dedicated to the work of judging, not ideology.". A leading Supreme Court scholar called Clark "the most underrated Justice in recent Supreme Court history." During his career, Clark balanced an underlying judicial restraint with a more expansive, yet principled reading of the Constitution and he demonstrated a rare capacity for change and growth. Justice William O. Douglas, with whom Clark served for all of his time on the Court, commented that Clark had "the indispensable capacity to develop so that with the passage of time he grew in stature and expanded his dimensions." Ultimately, Clark came to more fully understand, as he wrote in 1970, that the Constitution "is a living instrument which also must be construed in a manner to meet the practical necessities of the present." In
Merle Miller's book
Plain Speaking, based on interviews with President Truman, Miller attributes to Truman the statement that appointing Clark to the Court was his "biggest mistake" as president, adding, "He was no damn good as Attorney General, and on the Supreme Court . . . it doesn't seem possible, but he's been even worse." Allegedly asked by Miller to explain the comment, Miller quotes Truman as stating further: "The main thing is . . . well, it isn't so much that he's a bad man. It's just that he's such a dumb son of a bitch. He's about the dumbest man I think I've ever run across." Truman historians have challenged the accuracy and even the existence of a number of the quotes in the book, including the one about Clark. As one historian who listened to the original interview tapes noted, Miller "changed Truman's words in countless ways, sometimes thoughtfully adding his own opinions… Worst of all, Miller made up many dates in his book, inventing whole chapters." The purported comments also run counter to Truman and Clark's warm, personal relationship. No tape of the interview in which Truman and Miller discussed Clark is known to exist. ==Later life==