(Mandel Ngan/AFP/Getty Images)

The Supreme Court’s hearing Wednesday about the constitutionality of a lethal injection procedure turned into a tendentious, almost bitter battle between the court’s conservative and liberal justices.

Justice Samuel A. Alito Jr. accused those of trying to prevent the use of the drug midazolam as part of a lethal injection procedure in Oklahoma of waging a “guerrilla war against the death penalty.” Repeated challenges of lethal injection procedures, he said, were meant only to delay the implementation of executions.

Justice Antonin Scalia agreed, saying the “abolitionist movement” had put pressure on drug manufacturers to stop making available to states drugs that would ensure executions were not needlessly painful.

Justices Sonia Sotomayor and Elena Kagan were just as forceful on the other side. Kagan said that without proper sedation, the drug used to cause death was akin to being burned at the stake, except a person is being “burned alive from the inside.” Sotomayor told the Oklahoma solicitor general she would not believe assertions in his brief unless she verified them herself.

The Supreme Court heard arguments on the constitutionality of the lethal injection procedure, a case that stemmed from a botched execution in Oklahoma. (Reuters)

The questioning of Oklahoma’s Patrick R. Wyrick was so intense by the liberals that Chief Justice John G. Roberts Jr. granted him additional time at the podium. “Hopefully we will have a chance to hear what you have to say,” he said.

[Oklahoma recently made nitrogen gas its backup execution method]

These arguments came a year to the day after a botched execution in Oklahoma left an inmate writhing and grimacing on a gurney, drawing international attention to issues facing the lethal injection process in the United States.

The Oklahoma case centers on a particular drug that has been used by that state and others in executions that went awry last year. But it also touches on the reality that the capital punishment landscape in this country has fractured, pushing execution protocols further and further away from a method the court previously upheld.

The justices were revisiting the issue of lethal injection for the first time since 2008, when they upheld a three-drug combination and said it did not violate the Constitution’s ban on cruel and unusual punishment. At the time, these drugs were used across the country. But an ongoing shortage of lethal injection drugs fueled largely by European objections to capital punishment has caused states to struggle to find new drugs, create different protocols and seek other methods.

Until 2010, lethal injections in the United States were generally carried out using an anesthetic, a paralytic drug and a drug that stopped the heart, according to the Death Penalty Information Center. But a company that produced sodium thiopental, the anesthetic that was commonly used, stopped making the drug due to capital punishment. States began using another drug, pentobarbital, but the Danish company that supplied it said it would stop shipping it to U.S. prisons that executed inmates.

So states began adopting new and different drugs. In Oklahoma, when state officials could no longer obtain the drug they used to rely on, they turned to the drug midazolam. This particular drug was used in three problematic executions last year, turning it into a focal point for debates about lethal injections.

The most high-profile of these was Oklahoma’s bungled attempt to execute convicted murderer Clayton Lockett. The state used midazolam in one of its executions for the first time, and Lockett kicked, grimaced and survived for 43 minutes after the execution began. He eventually died after officials had already halted the process, and a state investigation blamed the bungled procedure on the execution team’s insertion of the needle during the injection.

Chief Justice John G. Roberts Jr. and Scalia both pointed out that there were issues with the administration of the drugs in Lockett’s execution. “If in fact the execution was not properly conducted, I don’t see how you can blame it on the — on the drug,” Scalia said.

Midazolam was also used last year in the execution of an Arizona inmate who gasped and snorted and took nearly two hours to die, as well as the lethal injection of an Ohio inmate who gasped and choked before dying after nearly half an hour.

“We’ve seen that lethal injection is not the swift, painless, effective method of causing death that it was made out to be,” said Robert Dunham, executive director of the Death Penalty Information Center. “The myth that you can swiftly and painlessly execute somebody in a manner that is humane and marginally civilized seems to have evaporated.”

Florida, the first state to use the drug in an execution, has utilized it numerous times without many witnesses reporting these kinds of issues; a media witness said that when the state first used the drug, the inmate being executed appeared to remain awake and moving for an unusually long period of time.

Ohio has since dropped midazolam from its protocol, and that state postponed its executions this year to give it time to adopt a new lethal injection practice. After the botched procedure last year, Oklahoma also changed its execution protocols, keeping midazolam but ramping up the dose to match the level used in Florida.

[What the Supreme Court’s decision here could mean for the death penalty]

The week before the justices decided to accept the lethal injection case, Oklahoma carried out its first execution since Lockett was put to death. The inmate, Charles Warner, who was convicted of raping and murdering an 11-month-old, had originally been set to die the same night as Lockett, but his execution was postponed.

The justices declined to stay that execution when the court’s four justices who wanted the execution stayed were overruled. However, it takes five justices to stay an execution, while it takes only four to accept a case. In the months since the Supreme Court said it would hear the challenge, states have carried out multiple executions.

Justice Sonia Sotomayor wrote in a dissent arguing for a stay that she found the idea that midazolam could “work as intended difficult to accept given recent experience with the use of this drug.”

Experts have said it is unclear whether midazolam can produce a deep enough level of unconsciousness to prevent an inmate from feeling pain from the injections that follow. In the briefs filed for this case, midazolam’s effectiveness takes center stage again and again.

The three Oklahoma death-row inmates arguing against the state’s protocol now argue in their filing to the court that using midazolam will cause them “excruciating pain and suffering during their executions.”

However, Scott Pruitt, the Oklahoma attorney general, and other state officials argue in their brief that this is not the case, instead painting this argument as an attempt to fight the death penalty under the guise of questioning one drug.

“Oklahoma’s lethal injection protocol does not present a substantial risk of severe pain and cannot be considered cruel,” the state officials wrote. In addition, the state also calls the attacks on midazolam “unwarranted” and says the higher dosage of the drug would cause unconsciousness during executions.

Pruitt said in a statement Wednesday after the arguments that he was confident the justices would uphold the state’s procedure.

More than a dozen professors of pharmacology had also submitted a brief to the court, taking no side in the case but writing that midazolam cannot be considered “an appropriate substitute” for the drugs that had been used to induce unconsciousness in executions.

Meanwhile, authorities in Florida — which has halted its own executions until the judges issue a decision — submitted a brief to the court agreeing with Oklahoma and saying that their state’s experiences show that midazolam can be used in humane executions.

The justices were facing questions of how to approach executions that involve substantially different protocols than the one they upheld in 2008, as well as whether condemned inmates should have to provide an available alternative if they object to an execution method.

In 2008, when the justices agreed to uphold the three-drug method, they did not all come to the same conclusions about the case or what could follow. Seven justices ultimately filed opinions in that case. Roberts, writing for the court, noted that there is always some risk inherent in an execution, but that alone does not make it unconstitutional.

“Simply because an execution method may result in pain, either by accident or as an inescapable consequence of death, does not establish the sort of ‘objectively intolerable risk of harm’ that qualifies as cruel and unusual,” he wrote.

Justice Clarence Thomas agreed with the outcome but not the reasoning, instead determining that a method of execution is only unconstitutional “if it is deliberately designed to inflict pain.”

Related: How the death penalty continued its slow, steady decline in 2014

[This post has been updated. First published: 8 a.m.]