A guard stands on the steps of the Supreme Court Building, August 20, 2014 in Washington, DC. (Photo by Mark Wilson/Getty Images)National Journal

The Supreme Court upheld a controversial execution method Monday, even as two justices said it's time to reconsider whether the death penalty is unconstitutional in the first place.

The justices were deeply, sometimes harshly divided in a 5-4 ruling that allows states to continue using the drug midazolam in lethal injections, despite its links to several botched executions. In a dissenting opinion, Justice Sonia Sotomayor said the court had left inmates "exposed to what may well be the chemical equivalent of being burned at the stake."

But while the case was ostensibly about one specific drug, it vividly exposed deep, fundamental divisions over capital punishment itself—between liberals who are ready to do away with it altogether and conservatives who think it's already too limited.

"Rather than try to patch up the death penalty's legal wounds one at a time, I would ask for full briefing on a more basic question: whether the death penalty violates the Constitution," Justice Stephen Breyer wrote in a dissenting opinion, joined by Justice Ruth Bader Ginsburg.

While Breyer acknowledged that the Court has upheld capital punishment in several past cases, he suggested that times have changed.

"The circumstances and the evidence of the death penalty's application have changed radically since then," he said. "Given those changes, I believe that it is now time to reopen the question."

Citing several academic studies, Breyer argued that the death penalty today is unreliable, arbitrary, subject to long delays, and not necessarily a good deterrent to violent crime.

Two members of the Court's conservative wing—Justices Antonin Scalia and Clarence Thomas—wrote separate decisions just to fight with Breyer. (Four justices—two from each side—read statements from the bench Monday, an extraordinary step with no recent precedent. Even in the most highly charged cases, two oral statements has always been the maximum.)

If the death penalty is applied inconsistently, Thomas said, that's the fault of death-penalty skeptics like Breyer. He criticized Supreme Court rulings that banned executing the mentally disabled, juveniles, and rapists.

"It seems to me that the best solution is for the Court to stop making up Eighth Amendment claims in its ceaseless quest to end the death penalty through undemocratic means," he said.

Scalia was especially scathing, dismissing Breyer's opinion as "a white paper devoid of any meaningful legal argument" and "full of "¦ gobbledy-gook.

"Capital punishment presents moral questions that philosophers, theologians, and statesmen have grappled with for millennia. The Framers of our Constitution ... left it to the People to decide," Scalia wrote. "By arrogating to himself the power to overturn that decision, Justice Breyer does not just reject the death penalty, he rejects the Enlightenment."

A more subtle form of that argument underscored the Court's specific holding on midazolam.

In short, the Court's conservative justices indicated that they've reached a breaking point with the tactics employed by death-penalty opponents. During oral arguments in the case, Justice Samuel Alito said critics were waging "what amounts to a guerilla war against the death penalty"—pressuring drug companies not to sell the safest anesthetics, which forces states to turn to riskier drugs like midazolam, which opponents then challenge in court as cruel and unusual.

That same frustration animated Friday's ruling.

"Because capital punishment is legal, there must be a constitutional means of carrying it out," Alito wrote for the Court's majority. He wrote that because the inmates in the case had not identified another, less risky alternative to Oklahoma's lethal-injection protocol, the state was free to use the best option it has.

Sotomayor disagreed vehemently.

"If all available means of conducting an execution constitute cruel and unusual punishment, then conducting the execution will constitute cruel and usual punishment," she said. "Nothing compels a State to perform an execution."

Midazolam is used as the first drug in a three-drug cocktail for some lethal injections. It's an anesthetic, designed to put inmates into a deep coma-like state so they can't feel the pain of the drugs that actually kill them. But it doesn't always work; on several occasions, inmates have woken up from the comas midazolam was supposed to induce, often writhing or screaming in pan.

Although capital punishment itself is not a violation of the Eighth Amendment, midazolam and other imperfect methods aren't necessarily constitutional just because inmates don't know whether a better alternative is out there, Sotomayor said.

"Under the Court's new rule, it would not matter whether the State intended to use midazolam, or instead to have petitioners drawn and quartered, slowly tortured to death, or actually burned at the stake: because petitioners failed to prove the availability of [other lethal-injection drugs], the State could execute them using whatever means it designated," Sotomayor argued. "The Eighth Amendment cannot possibly countenance such a result."

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