1940–1949: Supreme Court and military service
One year after becoming attorney general, on January 4, 1940, Murphy was nominated by President Roosevelt as Associate Justice of the Supreme Court, filling the vacancy caused by the death of Pierce Butler the previous November. He was confirmed by the United States Senate on January 16, and sworn in on February 5, 1940. The timing of the appointment put Murphy on the cusp of the Charles Evans Hughes and the Harlan F. Stone courts. On the death of Chief Justice Stone, Murphy served in the court led by Frederick Moore Vinson, who was confirmed in 1946. During World War II he served in the Army Reserve during three months of 1942 while the court was in recess. He served as the executive officer to the Chief of Staff of the United States Army George C. Marshall. He retired with the rank of Lieutenant Colonel.
Murphy took an expansive view of individual liberties, and the limitations on government he found in the Bill of Rights. He authored 199 opinions: 131 for the majority, 68 in dissent. One of the important opinions authored by Justice Murphy was Securities and Exchange Commission v. W. J. Howey Co. (1946), in which the Court defined the term "investment contract" under the Securities Act of 1933, thus giving content to the most important concept of what makes something a security in American law.
Opinions differ about him and his jurisprudential philosophy. He has been acclaimed as a legal scholar and a champion of the common man, but Justice Felix Frankfurter disparagingly nicknamed Murphy "the Saint", criticizing his decisions as being rooted more in passion than reason. It has been said he was "neither legal scholar nor craftsman", and he was criticized "for relying on heart over head, results over legal reasoning, clerks over hard work, and emotional solos over team play."
Murphy's support of African Americans, aliens, criminals, dissenters, Jehovah's Witnesses, Native Americans, women, workers and other "outsiders" evoked a pun: "tempering justice with Murphy." As he wrote in Falbo v. United States (1944), "The law knows no finer hour than when it cuts through formal concepts and transitory emotions to protect unpopular citizens against discrimination and persecution." (p. 561)
According to Frankfurter, Murphy was part of the more liberal "axis" of justices on the Court along with justices Wiley B. Rutledge, William O. Douglas, and Hugo L. Black; the group would for years oppose Frankfurter's "judicially restrained" conservative ideology. Douglas, Murphy and then Rutledge were the first justices to agree with Black's notion that the Fourteenth Amendment incorporated the Bill of Rights' protection in it; this view would later become law.
Murphy is perhaps best known for his vehement dissent from the court's ruling in Korematsu v. United States (1944), which upheld the constitutionality of the government's internment of Japanese-Americans during World War II. He sharply criticized the majority ruling as "legalization of racism."
This was the first time the word "racism" found its way into a Supreme Court opinion (Murphy had previously used the term twice in a concurring opinion in Steele v. Louisville & Nashville Railway Co. (1944) issued that same day). He would use that word again in five separate opinions before the word "racism" disappeared from Murphy's and the High Court's other opinions for almost two decades, not reappearing until the landmark decision of Loving v. Virginia (1967), which struck down as unconstitutional the Virginia anti-miscegenation statute. (See also Jim Crow laws.)
Although Murphy was serving on the Supreme Court during World War II, he still longed to be part of the war effort and so he served at Fort Benning, Georgia as an infantry officer during court recesses.
On January 30, 1944, almost exactly one year before Soviet liberation of the Auschwitz death camp on January 27, 1945, Justice Murphy unveiled the formation of the National Committee Against Nazi Persecution and Extermination of the Jews. Serving as committee chair, he declared that it was created to combat Nazi propaganda "breeding the germs of hatred against Jews." This announcement was made on the 11th anniversary of Adolf Hitler's appointment as Chancellor of Germany. The eleven committee members included U.S. Vice President Henry Wallace, 1940 Republican presidential candidate Wendell Willkie and Henry St. George Tucker, Presiding Bishop of the Protestant Episcopal Church.
Murphy was among 12 nominated at the 1944 Democratic National Convention to serve as Roosevelt's running mate in the presidential election that year. He acted as chairman of the National Committee against Nazi Persecution and Extermination of the Jews and of the Philippine War Relief Committee. The first committee was established in early 1944 to promote rescue of European Jews, and to combat antisemitism in the United States.