The U.S. Supreme Court on Monday approved the continued use of a sedative called midazolam in lethal injections, despite the controversy around a painful botched execution in Oklahoma last year. The petitioners in the case, Glossip v. Gross, are three Oklahoma death row inmates arguing the state’s execution drug cocktail constitutes cruel and unusual punishment.

A fourth man, Charles Warner, was originally part of the case—he was executed in January, just before a stay was granted pending appeal. Warner was initially scheduled to be put to death in April 2014, but his execution was delayed after Clayton Lockett’s lethal injection went horribly wrong.

Oklahoma’s controversial drug cocktail came into use after European manufacturers refused to provide the old drug of choice, sodium thiopental, to U.S. states for executions.

The vote was 5-4, with the conservative side of the court victorious and Justice Samuel Alito writing for the majority. Alito noted the inmates had the burden of proving midazolam was ineffective in inducing a coma and preventing the excruciating pain caused by the other two drugs in the cocktail, and he felt they failed:

The State’s expert presented persuasive testimony that a 500- milligram dose of midazolam would make it a virtual certainty that an inmate will not feel pain associated with the second and third drugs, and petitioners’ experts acknowledged that they had no contrary scientific proof.

The majority were persuaded by Oklahoma’s claim that Lockett’s botched death was caused by a failed IV, not by the drug involved.

In the principal dissent, Justice Sonia Sotomayor criticizes the majority for “deferring to the District Court’s decision to credit the scientifically unsupported and implausible testimony of a single expert witness” and for “faulting petitioners for failing to satisfy the wholly novel requirement of proving the availability of an alternative means for their own executions.”

Continuing to use midazolam as the only sedative for blocking out the searing pain of the other two drugs, she writes, “leaves petitioners exposed to what may well be the chemical equivalent of being burned at the stake.”

The Court also denied the three inmates a stay of execution that would give them time to prove Oklahoma’s lethal injection recipe is ineffective.

[Photo of Oklahoma execution chamber via AP Images]