The US Supreme Court on Wednesday agreed to halt the scheduled executions of three death-row plaintiffs who are challenging Oklahoma’s lethal injection protocol at the high court.

The case, likely to be argued in April, will examine whether Oklahoma’s three-drug protocol for lethal injection violates the Eighth Amendment prohibition on cruel and unusual punishment.

The stay orders were necessary to prevent the unusual possibility that all three death-row plaintiffs could, technically, be executed before their first legal brief arguing their case to the high court was even due on March 9.

Death-row inmate Richard Glossip was set to be executed Thursday. John Grant was scheduled for lethal injection on Feb. 19. Benjamin Cole was facing a March 5 execution.

Executing a death-row plaintiff before the court hears his case is not entirely unheard of. The Oklahoma case originally featured four death-row plaintiffs, but one was put to death before the Supreme Court agreed to take up the lethal injection case.

It is unclear why the justices did not issue a stay to prevent the Jan. 15 execution of that inmate, Charles Warner.

Nonetheless, the high court agreed a week later to hear the Oklahoma case, raising the question about whether stays should be issued to prevent the state from executing the three other plaintiffs while their case was pending before the court.

John Hadden, an Oklahoma assistant attorney general, asked for the stay and lawyers for the inmates agreed that pending executions should be halted.

Specifically at issue in the Supreme Court challenge is whether the first drug administered in the execution process – midazolam – is effective in rendering the condemned prisoner into a coma-like unconsciousness before the other two drugs are administered.

Lawyers for the inmates have expressed fear that if the first drug is ineffective, their clients will be subject to intense pain when the second and third drugs are administered.

The concerns were raised after botched executions in Oklahoma, Ohio, and Arizona last year. In all three cases, midazolam was the first drug used in a three-drug lethal injection protocol.

But the Oklahoma Attorney General’s Office didn’t just ask for a stay of execution. It also asked that the Supreme Court lift the stay and allow executions to move forward if the state Department of Corrections obtains a usable quantity of a substitute drug for midazolam. Two alternative drugs have been approved for use in the state’s three-drug lethal injection protocol.

In essence, the state has pledged not to use midazolam in any future executions until the Supreme Court resolves the pending case. But Oklahoma is continuing to search for usable quantities of the other two drugs.

If they are obtained, the state argued, “there would be no remaining impediment to carrying out petitioners’ executions.”

Robin Konrad, an assistant federal public defender representing the inmates, agreed in her brief to the court that the high court should order a halt to the imminent execution of her clients.

“If no stay is ordered, petitioners will be executed before the Court has a chance to review the merits of their case,” she wrote.

But the public defender objected to the second request from Oklahoma. If the plaintiffs are executed, their case before the high court would be rendered moot, short-circuiting any decision by the justices.

“This Court should not allow the important questions presented in this case to become moot only because the petitioners will be executed,” she wrote.

In its brief order on Wednesday, the court stayed the executions of the three plaintiff inmates, but only if those executions were to be carried out using midazolam.

A lawyer for the inmates praised the high court’s action in halting the imminent executions.

“We welcome today’s ruling staying executions in Oklahoma until the court can address serious questions about the state’s risky lethal injection protocol,” Dale Baich, an assistant federal public defender, said in a statement.

“Midazolam is an inappropriate drug to use in executions,” he said. “The scientific evidence tells us that even the proper administration of midazolam can result in an inhumane execution.”

The case is Glossip v. Gross (14-7955).