The retirement of Justice Anthony Kennedy from the U.S. Supreme Court after the 2017-2018 court term and his replacement with Justice Brett Kavanaugh marked a potentially pivotal change in the constitution of the Court with respect to death-penalty issues.

During Justice Kennedy’s thirty years on the Court, he became known as a swing vote, siding with both the conservative and liberal wings of the Court. His role as the Court’s swing vote extended to death-penalty cases, in which he provided the decisive fifth vote against a challenge to lethal-injection practices brought by Oklahoma death-row prisoners in Glossip v. Gross, but authored a number of key death-penalty decisions in favor of capital defendants.

Justice Kennedy was a leading architect of caselaw decided under the Eighth Amendment’s “evolving standards of decency.” Under that doctrine, the Court looked to various measures of contemporary American values to determine whether a national consensus had evolved against a penal practice. His 5-4 decisions included Roper v. Simmons (2005), in which the justices struck down the death penalty for juvenile offenders under age 18, Kennedy v. Louisiana (2008), in which the justices barred the death penalty for child rape and other offenses that did not result in death, Hall v. Florida (2014), striking down Florida’s use of a strict IQ threshold in determining whether defendants were intellectually disabled and therefore ineligible for the death penalty, and Panetti v. Quarterman, establishing the relevance of a prisoner’s mental illness in determining whether he or she is mentally competent to be executed.

In his opinion for the five-member majority in the Kennedy case, Justice Kennedy wrote: “When the law punishes by death, it risks its own sudden descent into brutality, transgressing the constitutional commitment to decency and restraint. For these reasons we have explained that capital punishment must ‘be limited to those offenders who commit a narrow category of the most serious crimes’ and whose extreme culpability makes them ‘the most deserving of execution.’”

In Hall v. Florida , Justice Kennedy described the importance of the Eighth Amendment, the risks of the death penalty, and the United States’ responsibility as a leader in the civilized world:

“The Eighth Amendment’s protection of dignity reflects the Nation we have been, the Nation we are, and the Nation we aspire to be. This is to affirm that the Nation’s constant, unyielding purpose must be to transmit the Constitution so that its precepts and guarantees retain their meaning and force.”

He concluded:

“The death penalty is the gravest sentence our society may impose. Persons facing that most severe sanction must have a fair opportunity to show that the Constitution prohibits their execution. Florida’s law contravenes our Nation’s commitment to dignity and its duty to teach human decency as the mark of a civilized world. The States are laboratories for experimentation, but those experiments may not deny the basic dignity the Constitution protects.”