The U.S. Supreme Court on Monday declined to hear a key Louisiana death-penalty case, as well as a parallel case from Missouri, both of which would have forced states to divulge where they acquired their lethal-injection drugs.

The moves come as the climate of capital punishment becomes increasingly tumultuous, with states scrambling for new ways to kill death row inmates amid lethal-injection drug shortages.

In the Louisiana case, death-row inmate Christopher Sepulvado argued he has a constitutional due-process right to know how he will be killed. Specifically, he and his attorneys want to know what drugs will be used and where they were manufactured and tested. They contend that poor-quality drugs could lead to a cruel and unusual punishment.

The Missouri case involved whether prisoners have to propose an alternative method of execution, but it also examined the provenance of the drugs.

In both instances, the court’s decisions mark the end for those particular legal efforts, and could allow states to continue to argue for secrecy when it comes to lethal injection.

Sepulvado has been involved in more than a year of court battles and has seen execution dates come and go. He was convicted in 1993 of torturing and killing his stepson.

The Supreme Court’s decision lets stand the U.S. Fifth Circuit Court of Appeals decision that Sepulvado does not have a due process right to know his execution protocol.

In the Missouri case, a district court required that the state Department of Corrections disclose the identities of the pharmacy, laboratory and physician prescribing the lethal injection drug.

The Eighth Circuit Court of Appeals said that Missouri’s court was in error requesting pharmacy information because it wasn’t relevant to inmate David Zink’s argument that his pending execution could result in a cruel and unusual death.

The Eighth Circuit added that the state could have trouble obtaining the lethal injection drugs if identities of suppliers are made public — an argument that Louisiana Department of Corrections officials have also made in legal filings.

“Our analysis must begin with a basic proposition: ‘[C]apital punishment is constitutional. It necessarily follows that there must be a means of carrying it out,’” the Eighth Circuit wrote.

The judges also shifted burden to the death-row inmate and said he failed to offer a constitutional means by which Missouri could execute inmates.

Zink was convicted of abducting, killing and burying a woman named Amanda Morton. He confessed that he kidnapped her after getting into a traffic accident with her, then tied her to a tree, broke her neck, stabbed her and buried her in a cemetery.

The issue of the source of the drugs, though, is still in play in federal court in Louisiana. The Fifth Circuit has ordered the state to provide information about the manufacturers of the drugs the state will use, and the state has said it doesn’t plan to appeal that ruling.

Other inmates nationwide have claimed they have a constitutional right to know how states intend to execute them.

When nation’s supply of drugs such as sodium thiopental and pentobarbital began to dwindle, states started turning to unorthodox or new methods of execution.

In Georgia, for example, officials began buying from a compounding pharmacy for a July 2013 execution. Compounding pharmacies aren’t always regulated by the Food and Drug Administration. Documentation revealed in January later raised the question whether or not the state obtained its drugs from a pharmacy that was considered for use by the Louisiana Department of Corrections.

In Ohio, officials used a new combinations of drugs in January, which led to an unusually long execution in which the condemned man convulsed and gasped for air.

So far, states have managed to obtain new death penalty drugs, but not without difficulty. In order to avoid bad publicity, companies have declined to sell drugs to states for lethal injection.

In response, states such as Louisiana have argued the need for secrecy, to be sure that they can keep replenishing supplies.

In an brief filed in support of Sepulvado’s petition to the Supreme Court, physicians and from across the nation called lethal injection methods “sheer speculation” that is highly imperfect and could therefore result in “human experimentation.”