When President Donald Trump returned to office in January 2025, he directed his administration to “restor[e] the death penalty.” His embrace of capital punishment helped fuel a surge in executions at the state level last year, as I previously reported, and led the Justice Department to produce a report on “strengthening” the federal death penalty, which was released late last month.
In the report, the Justice Department defended the use of pentobarbital – a powerful sedative – for lethal injections, criticizing the Biden administration’s determination that it may cause “unnecessary pain and suffering.” Nevertheless, citing ongoing legal challenges to pentobarbital use and related problems obtaining the drugs used in lethal injections, the DOJ recommended expanding the list of federal execution methods by adding firing squads, electrocution, and lethal gas.
Throughout the report, the Justice Department referenced past Supreme Court rulings in capital cases, noting that the court “has never rejected a method of execution as unconstitutional.” Left unsaid was a follow-on assumption: It’s unlikely to do so anytime soon.
If you explore SCOTUSblog’s record of requests for stays of execution, that may, at first, appear to be a safe assumption. The record shows that the court only rarely comments on – much less takes up for argument – issues raised by death row inmates, including challenges to execution methods. The court has not paused an execution in nearly two years, and, over that period, there have been only a handful of noted dissents.
But if you look closely at cases in which there was acknowledged disagreement among the justices, it’s clear that at least a few of them have serious questions about the constitutionality of one of the execution methods featured in the DOJ report: nitrogen hypoxia, or death as the result of inhaling pure nitrogen gas.
Execution by nitrogen gas
As the DOJ noted in its report, “lethal gas has a long history of use as a form of capital punishment in the United States.” In the past, such executions were typically carried out with cyanide gas, but today’s lethal gas executions use nitrogen.
In nitrogen gas executions, a mask dispensing pure nitrogen blocks access to oxygen, leading to death by hypoxia, or oxygen deprivation. The DOJ contended that “death by nitrogen hypoxia” has the support of “advocates of medically assisted suicide.” However, it acknowledged an ongoing debate over its risks, including that it may cause “conscious suffocation.”
Nitrogen hypoxia is an approved form of execution in five states: Alabama, Arkansas, Louisiana, Mississippi, and Oklahoma. But in some of these states, it can only be used if lethal injection drugs are not available or if an inmate affirmatively chooses it, according to the Death Penalty Information Center. The first nitrogen gas execution in the U.S. was carried out in Alabama, where lethal injection is the default method but inmates can choose nitrogen hypoxia or electrocution, in January 2024, and seven more have taken place since then – six in Alabama and one in Louisiana, according to the center’s records.
After the most recent nitrogen gas execution – Anthony Boyd’s death in Alabama on Oct. 23, 2025 – The New York Times highlighted growing concern about its use. While nitrogen hypoxia was introduced as a humane alternative to lethal injection at a time when policymakers, including in the Biden administration, were reassessing the use of pentobarbital, observers of nitrogen gas executions have “described difficult-to-watch scenes in which prisoners writhe on the gurney before they are pronounced dead.” The Times noted that “Lee Hedgepeth, a journalist in Alabama who witnessed” Boyd’s execution, saw “Boyd gasp for air more than 225 times before he was pronounced dead.”
In its report, the DOJ pointed to three rulings on nitrogen hypoxia – two from the U.S. Court of Appeals for the 11th Circuit and one from the U.S. Court of Appeals for the 5th Circuit, emphasizing that both courts held that this execution method “comports with the Eighth Amendment,” which prohibits “cruel and unusual punishments.” The 5th Circuit held that “[b]reathing 100% pure nitrogen causes unconsciousness in less than a minute, with death following rapidly within ten to fifteen minutes. And it does not produce physical pain.” It concluded, as the DOJ put it, that “death by nitrogen hypoxia was no more painful than other methods of execution already approved by the Supreme Court.”
Justices raise questions
The DOJ observed that the prisoners appealed those rulings from the 11th and 5th Circuits to the Supreme Court, which denied requests to pause the executions. It did not, however, add that there were public dissents in two of those cases, nor did the DOJ engage with the concerns those dissenting justices shared about nitrogen gas executions.
In fact, since January 2024, when Alabama carried out the first such execution, the court’s three Democratic-appointed justices – Sonia Sotomayor, Elena Kagan, and Ketanji Brown Jackson – have dissented in three capital cases involving nitrogen hypoxia, and Justice Neil Gorsuch has dissented in one. The three liberal justices questioned whether this method of execution violates the Eighth Amendment, while Gorsuch emphasized potential religious freedom concerns.
The first such writings came in Smith v. Hamm, in which Kenneth Eugene Smith challenged Alabama’s plan to make him the first person in the country to be executed by nitrogen hypoxia. Alabama had previously tried and failed to execute Smith by lethal injection due to issues accessing a vein, and, although he had previously expressed a preference for being executed via nitrogen gas, he contended in 2024 that Alabama’s plan for his second execution violated the Eighth Amendment. The Supreme Court declined to pause his execution, but Sotomayor, Kagan, and Jackson dissented from the denial. In her dissent, Sotomayor described nitrogen hypoxia as an “untested” method, raising the possibility that Smith might “choke[] on his own vomit” rather than dying of oxygen deprivation. “With deep sadness, but commitment to the Eighth Amendment’s protection against cruel and unusual punishment, I respectfully dissent,” Sotomayor wrote.
In her own brief dissenting opinion, joined by Jackson, Kagan contended that Alabama should have provided more information about its new protocol, explaining that she would put the execution on hold to give the court time “to address that important issue.”
The next separate writing on nitrogen hypoxia came in March 2025 in Hoffman v. Westcott, in which Jessie Hoffman, who was Buddhist, challenged his pending nitrogen gas execution in Louisiana under the Eighth Amendment and the Religious Land Use and Institutionalized Persons Act (a law protecting certain religious freedoms), contending that nitrogen gas execution would interfere with a significant spiritual practice: “meditative breathing at the time of death.” Buddhists, he explained, believe that “meditation and unfettered breath at the time of transition from life to death determines the quality of rebirth.” Sotomayor, Kagan, and Jackson noted that they would grant Hoffman’s request for a stay of execution, but they did not explain why. Gorsuch also dissented and wrote to explain his belief that the court should have sent the case back to the 5th Circuit for fuller consideration of Hoffman’s RLUIPA claim.
The third and final nitrogen hypoxia case with a separate writing was Boyd’s in October 2025. Boyd had asked the court to consider whether nitrogen gas execution constitutes cruel and unusual punishment and expressed a willingness to be executed by firing squad instead. The court denied his request to pause his execution. In a nine-page dissenting opinion, which was joined by Kagan and Jackson, Sotomayor invited readers to imagine suffocating to death. “You want to breathe; you have to breathe. But you are strapped to a gurney with a mask on your face pumping your lungs with nitrogen gas,” she wrote. “Your mind knows that the gas will kill you. But your body keeps telling you to breathe. That is what awaits Anthony Boyd tonight.”
Sotomayor went on to describe the seven nitrogen gas executions that had taken place by that point, contending that “firsthand accounts from those executions” paint a picture of a painful, extended death marked by “violent movements” and gasps for air. “Seven people have already been subjected to this cruel form of execution,” she wrote. “The Court should not allow Boyd to become the eighth.”
A possible future case
Because Gorsuch only dissented in the case involving a religious freedom claim, it does not appear that he has broader concerns about execution by nitrogen gas. Even if he does, four votes are not enough to grant a request for a stay of execution, where five are needed. However, if there were indeed four votes to pause an execution, another justice may be willing to provide a “courtesy fifth” out of recognition that just four justices need to vote in favor of a petition for review of it to be taken up on the merits (although, admittedly, this “courtesy fifth” practice has not been employed consistently, as SCOTUSblog reported in 2016). In other words, it’s conceivable that this issue could make it to the court’s oral argument docket if states continue to use it.
In any event, the issue may be back in front of the Supreme Court on its emergency docket as soon as next month, when Jeffrey Lee, who was sentenced to death for the murders of Jimmy Ellis and Elaine Thompson, is scheduled to be executed by nitrogen hypoxia in Alabama. “The execution date” of June 11 “was set as Lee has an ongoing federal lawsuit challenging the humaneness of the nitrogen execution method,” according to the Associated Press. Specifically, like several appellants before him, Lee contends that execution by nitrogen gas qualifies as cruel and unusual punishment.