The US Supreme Court on Wednesday considered whether the murder conviction of Richard Glossip, a death row inmate in Oklahoma, should be set aside due to a witness having given false testimony in court and state prosecutors having failed to disclose key information about the witness.

In 1997, a hotel maintenance worker named Justin Sneed beat his employer, Barry Van Treese, to death. Sneed then claimed that Glossip, the hotel’s manager at the time, orchestrated the murder. According to various court documents, Sneed was told he could avoid the death penalty by testifying against Glossip at trial. Sneed ultimately testified that Glossip had paid him $10,000 to commit the murder. Glossip maintained his innocence, but was ultimately convicted of first-degree murder and sentenced to death in 1998 for the murder.

Glossip has continued to fight ever since, including before the nation’s highest court. In 2015, he and other Oklahoma inmates challenged the state’s lethal injection protocol, claiming the use of the drug midazolam violated their Constitutional rights under the Eighth Amendment, which prohibits “cruel and unusual punishments.” The US Supreme Court rejected that challenge.

At issue in the present Supreme Court case is Sneed’s testimony. In particular, Sneed suffered from severe mental health struggles, for which he had been treated in the past. At trial, he denied ever having received psychiatric care — a claim that has since been disproved. In 2023, it was discovered that the prosecutors had not revealed Sneed had bipolar disorder and was prescribed lithium after he was arrested. Sneed had also reportedly told his attorney his testimony was a “mistake,” but this information was not revealed to the defense.

As asserted in an amicus brief submitted by the Innocence Project, a criminal justice reform advocacy group:

The State violated Richard Glossip’s right to due process… The State withheld material evidence that would have undercut the credibility of its key witness, Justin Sneed, by showing that he suffered from a serious psychiatric condition. And the State failed to correct Sneed’s false testimony … when he denied that he was under the care of a psychiatrist. Indeed, the State now agrees that Mr. Glossip is entitled to relief for this violation of his due process rights.

Previously, in June of 2022, 30 Reed Smith LLP lawyers published a report after investigating the legitimacy of Glossip’s conviction, raising concerns about the conviction, and in the following year, Glossip appealed for Oklahoma’s court to set aside his conviction. In April, Glossip sought to halt his execution planned for May 18, 2023 and his conviction returned to the district court. Attorney Gentner Drummond was investigating Glossip’s conviction in 2023 and backed Glossip’s appeal.

Drummond has stated that Glossip’s conviction depended on Sneed’s credibility. However, Justice Clarence Thomas implied faults in the investigation and said that the original prosecutors, Connie Smotherman and Gary Ackley, should have the opportunity to share their side.

Last month, the US Supreme Court upheld the execution of a Missouri man whose death sentence had been similarly controversial. Marcellus Williams was executed on Sep. 25 despite widespread concern surrounding the witness testimonies, prosecutorial practice, and evidence that led to his conviction.