On Thursday, the U.S. Supreme Court chose not to intervene in a contentious death penalty case from Alabama. Consequently, that evening, the state executed 54-year-old Anthony Todd Boyd at the William C. Holman Correctional Facility in Atmore. Boyd’s execution was carried out using nitrogen hypoxia, an unorthodox method that involves forcing the condemned to breathe nitrogen until death ensues.

Justice Sonia Sotomayor issued a passionate dissent, painting a vivid picture of the harrowing nature of suffocation and contrasting it with the state-mandated execution of Boyd. Her dissent highlighted the grim realities of this method of execution while illustrating her opposition to the death penalty as applied in this case.

The dissent notes the background of Boyd’s conviction, detailing his role in a 1993 murder where a man was burned alive over a $200 drug debt. Despite his conviction, Boyd maintained his innocence until the very end.

In his final moments, Boyd reportedly declared, “I didn’t kill anybody. I didn’t participate in killing anybody.” His last words, as reported by the Associated Press, also included a call for systemic change: “There can be no justice until we change this system.” He expressed gratitude and love to those advocating for reform, concluding with a hopeful message: “Let’s get it.”

Now imagine for that entire time, you are suffocating. 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. Your mind knows that the gas will kill you. But your body keeps telling you to breathe.

That is what awaits Anthony Boyd tonight. For two to four minutes, Boyd will remain conscious while the State of Alabama kills him in this way. When the gas starts flowing, he will immediately convulse. He will gasp for air. And he will thrash violently against the restraints holding him in place as he experiences this intense psychological torment until he finally loses consciousness. Just short of twenty minutes later, Boyd will be declared dead.

In the underlying death penalty case, Boyd was convicted of murder for helping burn a man alive over a $200 drug debt in 1993.

To the end, the since-executed man proclaimed his innocence.

“I didn”t kill anybody. I didn’t participate in killing anybody,” he said — his final words reported by the Associated Press. “There can be no justice until we change this system,” he also reportedly said, before expressing love to those fighting for that change and adding: “Let’s get it.”

Sotomayor’s nine-page dissent — joined by Justice Elena Kagan and Justice Ketanji Brown Jackson — appears to have somewhat undercounted the killing time required to finalize Boyd’s criminal case.

The nitrogen gas began flowing at around 5:57 p.m. on Thursday night and the literal curtain was closed on viewing the final moments of his life at 6:27 p.m., according to the AP’s death chamber account. The man exhibited “a long series of heaving breaths that lasted at least 15 minutes” and Boyd was finally pronounced dead at 6:33 p.m.

The longer-than-expected state-sanctioned death perhaps speaks to the basis on which Boyd’s emergency application for a stay was filed with the nation’s high court earlier this week.

In the Oct. 21, filing submitted to Justice Clarence Thomas, and then referred to court, Boyd’s capital attorneys argued the state’s method of punishment “constitute cruel and unusual punishment in violation of the Eighth Amendment.” In fact, the denied petition itself undercounted the length of time Boyd would “suffer” through the process of death by nitrogen hypoxia. The filing predicted the man would be subject to asphyxiation for “two to seven minutes.”

The dissenting justice has opposed Alabama’s foray into the use of nitrogen gas for killing death row inmates from the first such instance of its application early last year. On Thursday, Sotomayor took the opportunity to remark on the nascent advance in killing technology.

“Nitrogen hypoxia is a new method of execution,” the dissent goes on. “To carry out an execution using this method, prison officials force a condemned person to inhale pure nitrogen gas, which displaces the oxygen in that person’s lungs. Robbed of air in this way, the body’s instinctual urge to breathe kicks in. At the same time, the mind understands that breathing will result in death.”

While Boyd himself maintained his innocence, his attorneys only asked for an alternative method of releasing the mortal coil.

Sotomayor takes some of her fellow justices to task for declining to stay the execution. The dissenters would have directed the lower courts to accede to Boyd’s request for a quicker death.

“Boyd asks for the barest form of mercy: to die by firing squad, which would kill him in seconds, rather than by a torturous suffocation lasting up to four minutes,” the dissent continues. “The Constitution would grant him that grace. My colleagues do not.”

Turning to the Eighth Amendment’s prohibition against “cruel and unusual” punishments, Sotomayor begrudgingly engages in what she calls a “deeply troubling” and “macabre weighing” of killing methods.

To hear the dissent tell it, the trial court and the appellate court “failed to recognize the significant differences between the two methods of execution despite the factual record before them.”

Again, the dissent at length:

[T]he District Court ignored that, under its own assumptions, nitrogen hypoxia would superadd up to seven minutes of psychological pain beyond the ordinary anticipatory distress of an execution. Once the execution starts, a firing squad would render someone unconscious in three to six seconds; nitrogen hypoxia, on the other hand, lasts for minutes. There is a significant constitutional difference between three to six seconds of physical pain and terror and two to seven minutes of conscious suffocation with its associated psychological pain and terror. In gross numerical terms, nitrogen hypoxia risks extending the period of terror up to 140-fold.

In sum, Sotomayor says Boyd “more than made his case” under reigning high court precedent on alternative death-method selection.

But at least five members of the court’s conservative majority denied the petition without a word; no majority opinion was written.

“This Court thus turns its back on Boyd and on the Eighth Amendment’s guarantee against cruel and unusual punishment,” the dissent complains. “Because the Court should have instead granted a stay of execution and Boyd’s petition for certiorari, I respectfully dissent.”