(This summary includes only those cases he participated in deciding while on the Supreme Court, not while he was on the Ninth Circuit)
Key:
- GOOD = Kennedy voted to limit the death penalty or strengthen rights of the accused
- BAD = Kennedy voted pro-death
- MIDDLING = Kennedy’s vote was fairly neutral

BAD
South Carolina v. Gathers, 490 U.S. 805 (1989) (overruled by Payne v. Tennessee (1991)):
Held that any victim impact testimony in a death penalty sentencing phase must be directly related to the “circumstances of the crime.” Kennedy dissented and would have allowed victim impact statements about the victim’s personal characteristics.
*****
BAD
Stanford v. Kentucky, 492 U.S. 361 (1989) (overruled by Roper v. Simmons (1991)):
Held that it was constitutional to execute anyone over the age of 16. Kennedy joined Scalia’s majority opinion that focused on the fact that people as young as 14 were executed at the time of the country’s founding.
*****
MIDDLING
Penry v. Lynaugh, 492 U.S. 302 (1989) (overruled by Atkins v. Virginia (2002)):
Held that it was constitutional to execute “mentally retarded” people. Kennedy joined O’Connor’s majority opinion only as it held that the claim was procedurally barred and that the insanity defense would likely prevent execution of “idiots,” so a separate protection was not needed.
*****
BAD
Walton v. Arizona, 497 U.S. 639 (1990) (overruled in part by Ring v. Arizona (2002)):
Held that it was constitutional for judges to make determinations about aggravating factors in a death penalty sentencing proceeding and that “especially heinous, cruel, or depraved…” is not too vague as an aggravating factor. Kennedy joined White’s plurality opinion and allowed judges to make death penalty sentencing decisions.
*****
BAD
Payne v. Tennessee, 501 U.S. 808 (1991):
Overruled Gathers and held that victim impact statements are constitutional and may be considered in death penalty sentencing proceedings. Kennedy joined Rehnquist’s majority opinion allowing victim impact statements and also joined concurring opinions by O’Connor, Scalia, and Souter, which addressed various other points.
*****
GOOD
Morgan v. Illinois, 504 U.S. 719 (1992):
Held that a capital defendant may challenge a prospective juror who states that he or she would automatically vote in favor of the death penalty in any case, just as the prosecution can challenge a prospective juror who would never impose the death penalty in any case. Kennedy joined White’s majority opinion allowing these defendant-initiated challenges.
*****
BAD/MIDDLING
Herrera v. Collins, 506 U.S. 390 (1993):
Held that evidence of actual innocence does not entitle a prisoner to relief from federal courts or, in some cases, from state courts. Kennedy joined Rehnquist’s majority opinion (BAD) blocking judicial relief in actual innocence cases and also joined O’Connor’s concurrence (MIDDLING) arguing that it would be unconstitutional to execute an actually innocent person, but that Herrera was not innocent.
*****
BAD
Schlup v. Delo, 513 U.S. 298 (1995):
Held that a death row prisoner’s actual innocence claim is subject to a lower procedural bar when there was a constitutional error at his trial than when there was no error at trial. Kennedy joined Rehnquist’s dissent and would have subjected these claims to the highest possible procedural bar.
*****
BAD
Harris v. Alabama, 513 U.S. 504 (1995):
Held that it is constitutional for a judge to make a death penalty sentencing decision as long as he or she considers the jury’s “advisory recommendation.” Kennedy joined O’Connor’s majority opinion and allowed judges, rather than juries, to impose death sentences.
*****
GOOD
Ring v. Arizona, 536 U.S. 584 (2002) (overruling in part Walton v. Arizona (1990)):
Held that it is an unconstitutional violation of the Sixth Amendment for a judge to engage in fact-finding by determining whether aggravating factors existed in a capital case. Kennedy joined Ginsburg’s majority opinion which required that a jury must make the determination of whether aggravating factors existed.
*****
GOOD
Atkins v. Virginia, 536 U.S. 304 (2002) (overruling Penry v. Lynaugh (1989)):
Held that it is unconstitutional to execute “mentally retarded” people because a national consensus against doing so had developed, which indicated “evolving standards of decency.” Kennedy joined Stevens’s majority opinion blocking the execution of people with intellectual disabilities without setting out a standard for determining who qualifies.
*****
BAD
Schriro v. Summerlin, 542 U.S. 348 (2004):
Held that the Ring decision does not apply retroactively to cases that have already completed the direct appeal process. Kennedy joined Scalia’s majority opinion blocking retroactive application because the absence of the rule does not “seriously diminish” the likelihood of an accurate conviction.
*****
GOOD
Roper v. Simmons, 543 U.S. 551 (2005) (overruling Stanford v. Kentucky (1989), et al.):
Held that it is unconstitutional to execute people for crimes committed before the age of 18. Kennedy wrote the majority opinion and argued that evolving standards of decency, sociological research, and a national consensus militated against executing minors.
*****
BAD
Oregon v. Guzek, 546 U.S. 517 (2006):
Held that capital defendants do not have a right to introduce new evidence of their innocence during the sentencing phase of a death penalty trial if the evidence was not introduced during the guilt phase. Kennedy joined Breyer’s majority opinion imposing this restriction on potential proof of innocence.
*****
GOOD
Hill v. McDonough, 547 U.S. 573 (2006):
Held that a death row prisoner can properly challenge a state’s execution method in a §1983 civil rights lawsuit even if he had previously instituted federal habeas corpus proceedings. Kennedy wrote the decision for a unanimous Court.
*****
BAD
Kansas v. Marsh, 548 U.S. 163 (2006):
Held that it is constitutional to impose a death sentence when the aggravating and mitigating factors balance out evenly and were viewed as being of equal weight. Kennedy joined Thomas’s majority opinion establishing (essentially) that a tie can lead to death.
*****
BAD
Medellín v. Texas, 552 U.S. 491 (2008):
Held that the U.N. Charter, Vienna Convention, and International Court of Justice rulings are not binding in the context of consular access issues because the relevant treaty was not self-executing. Kennedy joined Roberts’s majority opinion which allowed Medellín, a Mexican citizen, to be executed despite never having been allowed access to his government’s consular officials.
*****
BAD
Baze v. Rees, 553 U.S. 35 (2008):
Held that lethal injection with sodium thiopental is “humane and constitutional” and also that “an isolated mishap alone does not violate the Eighth Amendment.” Kennedy joined Roberts’s plurality opinion allowing executions to proceed with sodium thiopental.
*****
GOOD
Kennedy v. Louisiana, 554 U.S. 407 (2008):
Held that the death penalty may not be imposed for child rape where death did not occur and death was not intended. Kennedy wrote the majority opinion and argued that there was no national consensus in favor of the death penalty for child rape because only six states allowed it, the punishment was not proportional, and that the death penalty should not imposed for crimes that did not result in death.
*****
GOOD
Harbison v. Bell, 556 U.S. 180 (2009):
Held that indigent death row prisoners are entitled to federally appointed counsel to represent them in state clemency proceedings where states have refused to provide counsel. Kennedy joined Stevens’s majority opinion allowing federal defenders to represent clients in state clemency proceedings.
*****
BAD
Leal Garcia v. Texas, 564 U.S. 940 (2011) (per curiam):
Held that courts cannot stay an execution on the basis of a statute that may or may not be passed in the future, in this case a statute requiring Vienna convention consular access procedures to be followed. Because the decision was issued per curiam, we do not know which justice wrote it, but we do know that Kennedy did not dissent.
*****
GOOD
Hall v. Florida, 572 U.S. ___ (2014) (clarifying Atkins v. Virginia (2002)):
Held that rigid IQ-based standards are unconstitutional for purposes of death penalty eligibility and required states to look beyond IQ tests when the score is within a margin of error. Kennedy wrote the majority opinion and blocked the application of these rigid standards.
*****
BAD
Glossip v. Gross, 576 U.S. ___ (2015):
Held that midazolam executions are not cruel and unusual punishment and also that prisoners must propose a known and available alternative method of execution before challenging lethal injection. Kennedy joined Alito’s majority opinion that allowed botched executions to continue.
*****
GOOD
Hurst v. Florida, 577 U.S. ___ (2016):
Held that a jury must make the actual factual findings regarding aggravating factors for purposes of capital sentencing and that jury “recommendations” are not sufficient. Kennedy joined Sotomayor’s majority opinion reaffirming the application of Ring and Apprendi.