William J. Brennan Jr. - Wikipedia

Shortly before the 1956 presidential election, President Dwight D. Eisenhower used a recess appointment to place Brennan on the Supreme Court. Brennan won Senate confirmation the following year.

Due to his ability to shape a wide variety of opinions and bargain for votes in many cases, he was considered to be among the Court's most influential members. Associate Justice Antonin Scalia, who served alongside Brennan between 1986 and 1990, called Brennan "probably the most influential Justice of the [20th] century."[4][5]

Brennan strongly believed in the Bill of Rights, arguing early on in his career that it should be applied to the states in addition to the federal government.[41] He often took positions in favor of individual rights against the state, favoring criminal defendants, minorities, the poor, and other underrepresented groups.

Furthermore, he generally shied away from the absolutist liberal positions of Justices Hugo Black and William O. Douglas, being very amenable to compromise in order to win a majority of Justices.[42]

he believed that the deliberate taking of human life by the state, as a punishment, was inherently cruel and unusual.

In Glass, the Court chose not to hear a case that challenged the constitutionality of the use of the electric chair as a form of execution. Brennan wrote:[47]

Th[e] evidence suggests that death by electrical current is extremely violent and inflicts pain and indignities far beyond the "mere extinguishment of life". Witnesses routinely report that, when the switch is thrown, the condemned prisoner "cringes," "leaps," and "fights the straps with amazing strength." "The hands turn red, then white, and the cords of the neck stand out like steel bands." The prisoner's limbs, fingers, toes, and face are severely contorted. The force of the electrical current is so powerful that the prisoner's eyeballs sometimes pop out and "rest on [his] cheeks." The prisoner often defecates, urinates, and vomits blood and drool.

Brennan concluded by stating that electrocution is "nothing less than the contemporary technological equivalent of burning people at the stake."

Brennan wrote the majority opinion in Roth v. United States which set new standards for obscenity laws, allowing some prosecutions, but drastically loosening the laws overall.[48] He later reversed his position in dissent in Miller v. California arguing that obscenity laws were unconstitutional.

He is regarded as one of the most liberal justices in the history of the court.[54]