On Tuesday, Attorney General Eric H. Holder Jr. said he supported the idea of halting all lethal injections in the United States until after the Supreme Court issues a ruling on the issue. The Supreme Court is hearing a case about lethal injection in Oklahoma this spring, with a ruling expected in the summer, to determine if that state’s procedures are constitutional.

“From my perspective, I think a moratorium until the Supreme Court made that determination would be appropriate,” Holder said during remarks at the National Press Club in Washington, D.C.

This idea has been raised before in the weeks since the justices said they would hear a lethal injection case. In court filings and orders, in arguments and motions, attorneys and judges and justices have questioned whether any executions should take place when it is known that the Supreme Court is going to rule on the issue very soon. Yet the suggestion does not seem to be taking. While four executions have been postponed due to this particular case, this has not translated into a broader moratorium.

Holder noted that he was speaking personally, rather than as a government official, in making his pronouncement, and he has said in the past he is opposed to the death penalty. He said his opposition centered on “the ultimate nightmare” of someone being executed due to a mistake, something he described as an “inevitable” feature of a death penalty system that relies on the fallible judgments of human beings.

“There’s always the possibility that mistakes will be made,” he said Tuesday. “Mistakes and determinations made by juries, mistakes in terms of the kind of representation somebody facing a capital offense receives….There is no ability to correct a mistake where somebody has, in fact, been executed.”

The fact that there is currently no moratorium points to the differences between the last time the Supreme Court considered lethal injection and the current case. The Oklahoma case represents the Supreme Court’s first examination of lethal injection — the primary method of execution in the United States — since 2008. That ruling ended what had become a de facto moratorium on executions, because it involved a form of lethal injection used by dozens of states. In the years that followed, the lethal injection landscape, and by extension the capital punishment landscape, has dramatically shifted in the United States, leaving the justices with a very different situation.

When the court acted in the Baze v. Rees decision in 2008, it upheld a form of lethal injection that has since become obsolete, because a drug shortage has caused the dwindling number of states still carrying out executions to scramble and improvise in an attempt to execute inmates. At the time, the court’s action meant that the lethal injection protocol used by dozens of states was acceptable. The Oklahoma case, meanwhile, seems to center on the use of the drug midazolam, which has been involved in three problematic executions but has not found widespread adoption; it has been used in just 15 of the 82 executions carried out since the beginning of 2013, almost all of them in Florida. (One of those problematic executions occurred in Ohio, which said it will no longer use midazolam and delayed all executions scheduled for this year so it can find new lethal injection drugs.)

“It was a different issue in that all states were using essentially the same method, whereas now it’s a more specific and narrow case that the court has taken,” Richard Dieter, executive director of the Death Penalty Information Center, said in an interview Wednesday.

When the court acted in 2008, it dissolved a de facto moratorium and allowed a surge of executions to begin in the country. There were no executions between the end of September 2007 and early May 2008, the period between the court’s decision to hear the case and its ruling. Dozens of executions occurred in the months after the Baze decision, and in 2009, the first full year following that decision, states carried out 52 executions. (That number has since dropped, falling to 35 executions last year, the lowest annual total in two decades.)

States soon began dealing with a drug shortage caused by European objections to the death penalty, a situation that meant the three-drug combination they had previously used was replaced by a patchwork system where different states use varying drugs or combinations. That, in turn, has been followed by problems with executions; an inmate in Oklahoma grimaced and kicked during his execution last spring, three months before an Arizona inmate gasped, snorted and took nearly two hours to die. Both of these executions, along with the lengthy lethal injection in Ohio last year, involved midazolam, a drug questioned by Justice Sonia Sotomayor in a dissent the week before the Supreme Court said it would take the lethal injection case.

In the time since the Supreme Court said it would consider lethal injection, voices at various levels of the process have considered whether executions should be delayed until after the justices rule. The Supreme Court, at the request of Oklahoma, said it was staying three executions scheduled in that state until the justices ruled. The court also declined to stay a Missouri execution that had cited the coming Oklahoma decision. (Missouri has used midazolam to sedate inmates before executions, but has not used it as one of the lethal drugs.) The Florida Supreme Court this week said it was staying an execution scheduled there because the state’s execution protocol and the one used in Oklahoma use the same amount of midazolam.

“The standards the Supreme Court are going to lay out, certainly they’re going to focus on midazolam, but they’re going to give a blueprint for any new, untried method,” Dieter said. “That could affect every state. We are in an uncertain period with lethal injection drugs.”

There are currently 10 executions scheduled between now and the beginning of oral arguments in the Oklahoma case at the end of April. Seven of them are in Texas, with the other three set for Missouri, Georgia and Tennessee.

The Texas Department of Criminal Justice “does not intend to delay executions” due to the Supreme Court’s review of Oklahoma, Robert C. Hurst, a spokesman, said in a statement Wednesday. “The agency does not use the same drug combination, but instead utilizes a single, lethal dose of pentobarbital to carry out executions,” Hurst said. “The agency has used this protocol since 2012 and has carried out 39 executions without complication.”

Missouri’s Department of Corrections said it remains prepared to carry out an execution next month, noting that the execution warrants in that state are issued by the Missouri Supreme Court. The Georgia and Tennessee Departments of Corrections did not respond to requests for comment on Wednesday.

While other court action or government intervention could affect some of these executions, it appeared unlikely the country’s highest court would step in. Just a week before Holder spoke, an inmate in Missouri who argued that his execution should be postponed while the Supreme Court considers lethal injection was put to death after the justices declined to step in. The situation pointed to how divided the court is as well as a quirk of how the court operates: The four justices who dissented from a decision allowing an Oklahoma execution to go forward last month are the same four who would have stayed the Missouri execution. While it takes five justices to stay an execution, only four are needed to accept a case.