Capital punishment is the government-imposed death penalty for certain serious crimes, authorized under federal law and in 27 states, though four of those states have paused executions through governor-imposed moratoriums. The Eighth Amendment sets the outer limit on the practice, forbidding cruel and unusual punishment and requiring that both the sentencing procedure and the execution method meet what the Supreme Court calls “evolving standards of decency.”1Legal Information Institute. U.S. Constitution – Eighth Amendment A death sentence can only be imposed for a narrow category of crimes, decided through a specialized two-phase jury trial, and carried out only after years of mandatory review.
The modern system was built after the Supreme Court struck down every existing death penalty statute in 1972 for being arbitrary and discriminatory in application,2Justia U.S. Supreme Court Center. Furman v. Georgia, 408 U.S. 238 (1972) then upheld Georgia’s rewritten statute four years later. That 1976 ruling introduced the guided, two-phase sentencing structure that every death penalty jurisdiction still uses today.3Justia U.S. Supreme Court Center. Gregg v. Georgia, 428 U.S. 153 (1976)
What Crimes Can Lead to a Death Sentence
At the state level, nearly every jurisdiction limits capital punishment to first-degree murder accompanied by at least one statutory aggravating factor. The specific aggravators vary by state but typically include the murder of a law enforcement officer, a killing committed during another serious felony, murder for hire, and killings involving multiple victims. An ordinary murder conviction, standing alone, is not enough.
The Federal Death Penalty Act of 1994 governs federal capital charges. It covers treason, espionage, and large-scale drug trafficking through a continuing criminal enterprise that meets specific quantity or revenue thresholds.4Office of the Law Revision Counsel. 18 U.S.C. 3591 – Sentence of Death It also reaches drug enterprise leaders who attempt to kill witnesses, jurors, or public officials, as well as federal homicides committed in connection with kidnapping, terrorism, or attacks on government officials.5Office of the Law Revision Counsel. 18 U.S.C. 3592 – Mitigating and Aggravating Factors to Be Considered in Determining Whether a Sentence of Death Is Justified Federal capital charges can be brought regardless of where the crime took place, including in states that have abolished the death penalty.
There is a firm constitutional limit on non-homicide offenses against individuals. In 2008, the Supreme Court held that the Eighth Amendment bars a death sentence for the rape of a child when the crime did not result in, and was not intended to result in, the victim’s death.6Justia U.S. Supreme Court Center. Kennedy v. Louisiana, 554 U.S. 407 (2008) The reasoning extends broadly to any crime against an individual victim that stops short of killing. Federal offenses like treason and espionage survive the limit because they are classified as crimes against the state. Military-specific offenses sit in their own category, discussed further below.
How a Capital Case Is Tried and Sentenced
Every capital case proceeds in two separate phases before the same jury. The first phase decides guilt or innocence, like any other criminal trial. If the jury convicts, the case moves to a penalty phase where the jury hears additional evidence and decides between death and life imprisonment.7Office of the Law Revision Counsel. 18 U.S.C. 3593 – Special Hearing to Determine Whether a Sentence of Death Is Justified The split exists to keep gruesome sentencing-phase evidence out of the guilt deliberations.
During the penalty phase, the prosecution presents aggravating factors — circumstances that make the crime or defendant especially deserving of death. Under federal law, these include prior violent felonies, creating a grave risk of death to others, and committing the murder in a particularly heinous or cruel manner.5Office of the Law Revision Counsel. 18 U.S.C. 3592 – Mitigating and Aggravating Factors to Be Considered in Determining Whether a Sentence of Death Is Justified The defense presents mitigating factors: anything about the defendant’s background, character, or mental state that argues for a lesser sentence. Aggravating factors require a unanimous jury finding. Mitigating factors do not; each juror can independently decide a mitigator applies.7Office of the Law Revision Counsel. 18 U.S.C. 3593 – Special Hearing to Determine Whether a Sentence of Death Is Justified
If the jury finds no aggravating factors, the court must impose a sentence other than death. If aggravators are found, the jury weighs them against the mitigating evidence to decide whether death is justified. The Sixth Amendment requires that a jury, not a judge, find each fact necessary to make a defendant eligible for the death penalty.8Justia U.S. Supreme Court Center. Hurst v. Florida, 577 U.S. 92 (2016) Most death penalty jurisdictions also require a unanimous jury vote at both phases, though a handful of states let judges make the final sentencing call after a jury determines eligibility, or step in when the jury deadlocks.
Who the Constitution Exempts From Execution
Three categories of people cannot be executed even when their offense would otherwise qualify.
People With Intellectual Disabilities
The Supreme Court held in 2002 that executing a person with an intellectual disability violates the Eighth Amendment.9Justia U.S. Supreme Court Center. Atkins v. Virginia, 536 U.S. 304 (2002) The clinical standard the Court referenced requires three elements: significantly below-average intellectual functioning, substantial limitations in adaptive skills such as communication and self-care, and onset before age 18. States set their own procedures for identifying who meets the standard, which has produced ongoing litigation over IQ cutoffs and the role of clinical judgment.
People Who Were Under 18 at the Time of the Crime
In 2005, the Court held that the Constitution forbids executing anyone who was under 18 when the offense occurred.10Justia U.S. Supreme Court Center. Roper v. Simmons, 543 U.S. 551 (2005) The Court pointed to the developmental immaturity of minors: more impulsivity, more vulnerability to outside pressure, and characters that are not yet fully formed. Those traits translate into diminished moral culpability.
People Who Are Incompetent at the Time of Execution
Even a lawfully sentenced prisoner cannot be executed if they currently lack the mental capacity to understand their punishment and why it is being imposed. The rule comes from a 1986 decision rooted in common law tradition.11Justia U.S. Supreme Court Center. Ford v. Wainwright, 477 U.S. 399 (1986) Competency for execution is evaluated right before the scheduled date, not at the time of the crime. If a prisoner becomes incompetent while on death row, the state must halt the execution and conduct a competency hearing; the sentence can only be carried out if competency is restored.
How Executions Are Carried Out
Lethal injection is the default method in the federal system and in every state that authorizes the death penalty. The federal protocol uses a single drug, pentobarbital.12United States Department of Justice. The Justice Department Takes Actions to Strengthen the Federal Death Penalty State protocols differ; some use a single drug, others a multi-drug sequence meant to induce unconsciousness, then paralysis, then cardiac arrest. Litigation over whether specific drug combinations create an unacceptable risk of severe pain has made lethal injection the most legally contested method.
Many states authorize backup methods in case lethal injection is unavailable or struck down. These include electrocution, lethal gas, hanging, and the firing squad, which the federal government added as an authorized method as of 2026.12United States Department of Justice. The Justice Department Takes Actions to Strengthen the Federal Death Penalty The newest authorized method is nitrogen hypoxia, which replaces the oxygen the condemned person breathes with pure nitrogen. Alabama carried out the first-ever nitrogen hypoxia execution in January 2024. As of 2026, Alabama, Louisiana, Mississippi, and Oklahoma authorize nitrogen hypoxia, most as a backup to lethal injection, and Arkansas added nitrogen gas by legislation in 2025.
All methods remain subject to Eighth Amendment challenge. The Supreme Court has never declared any particular method categorically unconstitutional, but state courts have struck down specific protocols.
Where Capital Punishment Applies
Twenty-seven states have death penalty statutes on the books. Four of those — California, Ohio, Oregon, and Pennsylvania — have governor-imposed moratoriums that suspend executions while the laws technically remain in force. That leaves roughly 23 states currently willing and able to carry out an execution. Even within active states, use is uneven: a small number of counties account for a disproportionate share of death sentences.
Recent years have moved toward abolition. Colorado ended its death penalty in 2020, Virginia in 2021, Washington’s legislature formally removed its statute in 2023 after the state supreme court had already declared it unconstitutional in 2018, and Delaware completed the same legislative process in 2024.
The federal government can seek capital punishment for any qualifying federal offense anywhere in the country, including in abolitionist states. Any federal capital prosecution must be authorized by the Department of Justice before a U.S. Attorney can pursue it. The Uniform Code of Military Justice authorizes the death penalty for several military offenses, including desertion during wartime,13Office of the Law Revision Counsel. 10 U.S.C. Chapter 47 – Uniform Code of Military Justice mutiny and sedition,14Office of the Law Revision Counsel. 10 U.S.C. 894 – Art. 94. Mutiny or Sedition and espionage involving nuclear weapons, war plans, or other critical defense systems. Any death sentence imposed by a court-martial must be approved by the President. No military execution has been carried out in decades, but the framework remains active.
What Happens After a Death Sentence
Capital cases go through more layers of review than any other criminal proceeding. More than half of the people currently on death row in the United States have been there over 18 years. That timeline reflects a multi-stage review process built to catch errors before an irreversible punishment is carried out.
Direct Appeal
Every death sentence triggers an automatic appeal to the state’s highest court, or in federal cases to the appropriate federal appellate court. Review at this stage is limited to issues on the trial record: sufficiency of the evidence, legal errors by the judge, and jury instructions. The appellate court can uphold the conviction and sentence, reverse the conviction, or overturn the death sentence while leaving the conviction intact.
State Post-Conviction Review
After direct appeal, the defendant can file for state post-conviction relief, sometimes called collateral review. This stage allows claims that go beyond the trial record, including ineffective assistance of counsel, juror misconduct, and newly discovered evidence. These petitions start in the original trial court and move up through the state appellate system. Strict filing deadlines apply, and missing one can permanently bar a claim.
Federal Habeas Corpus
Once state remedies are exhausted, a death row prisoner can petition a federal court for a writ of habeas corpus, asking a federal judge to review whether the state conviction or sentence violated federal constitutional rights. Under the Antiterrorism and Effective Death Penalty Act, prisoners generally have one year from the date their conviction becomes final to file.15Office of the Law Revision Counsel. 28 U.S.C. 2244 – Finality of Determination The statute severely limits second or successive petitions, so a prisoner who fails to raise a claim in the first filing may be permanently blocked from raising it later, even if the claim wasn’t ripe at the time. The clock pauses while a “properly filed” state post-conviction petition is pending, but if a state court decides that filing was procedurally defective, the clock may have been running the whole time.
Executive Clemency
Clemency is the final safety valve and operates outside the courts. For federal death sentences, the President can grant a pardon, commute the sentence, or issue a reprieve. The Office of the Pardon Attorney reviews applications and makes recommendations, but the President’s decision is discretionary and unreviewable by any court.16U.S. Department of Justice. Office of the Pardon Attorney At the state level, every state constitution grants clemency authority to the governor, a board of pardons, or some combination. States that use a formal board process tend to grant clemency more often than those that vest the power solely in the governor. Across the board, clemency in capital cases is rare.
Cost and Exonerations
Death penalty cases are far more expensive than comparable cases where prosecutors seek life without parole. Multi-state studies have found capital cases cost between 2.5 and 5 times more than non-capital murder prosecutions, with some jurisdictions spending over $1 million more per case. The added cost comes from every stage: pretrial investigation, longer jury selection, the bifurcated trial, mandatory appeals, and years of post-conviction litigation. Most of that cost falls on taxpayers, because nearly all capital defendants are represented by public defenders or court-appointed counsel.
Since 1973, at least 200 people sentenced to death in the United States have later been exonerated. That number is part of why the system invests so heavily in post-conviction review, and part of why the debate over capital punishment has not quieted even as the number of states carrying it out has shrunk.