Marcellus Williams, the Missouri death row inmate who has maintained his innocence for nearly 24 years, is scheduled to be executed Tuesday, a day after the governor and the state Supreme Court refused to intervene.

Williams, 55, was convicted of killing Felicia Gayle, a former newspaper reporter found stabbed to death in her home in 1998, but he has long insisted he is innocent.

He is set to be executed by lethal injection at 6 p.m. CT Tuesday at the state prison in Bonne Terre unless the US Supreme Court intervenes.

The case raises the specter of potentially putting an innocent person to death, an inherent risk of capital punishment. At least 200 people sentenced to death since 1973 were later exonerated, four of them in Missouri, according to the Death Penalty Information Center.

The NAACP and the Council on American-Islamic Relations have called on Gov. Mike Parson to halt Williams’ execution.

Missouri Supreme Court declines to halt execution at 11th hour

Over the weekend, Williams’ lawyers and St. Louis County Prosecuting Attorney Wesley Bell filled a joint brief asking the state Supreme Court to send the case back to a lower court for a “more comprehensive hearing” on Bell’s January motion to vacate Williams’ 2001 conviction and sentence.

The St. Louis Prosecuting Attorney’s Office, which handled the 2001 trial against Williams, argued in the January motion that DNA testing of the murder weapon could exclude Williams as Gayle’s killer. But the argument fell apart last month at a circuit court hearing when new DNA testing revealing the murder weapon had been mishandled, contaminating the evidence meant to exonerate Williams and complicating his quest to prove his innocence.

And at Monday’s hearing, the Missouri Supreme Court declined to halt Williams’ execution.

Ultimately, the state Supreme Court unanimously decided not to halt the execution because the prosecutor “failed to demonstrate by clear and convincing evidence Williams’ actual innocence or constitutional error at the original criminal trial that undermines the confidence in the judgment of the original criminal trial,” the opinion read. The opinion also stated “because this Court rejects this appeal on the merits, the motion for stay of execution is overruled as moot.”

“Mr. Williams has exhausted due process and every judicial avenue, including over 15 hearings attempting to argue his innocence and overturn his conviction,” Parson said in a statement after the decision.

“No jury nor court, including at the trial, appellate, and Supreme Court levels, have ever found merit in Mr. Williams’ innocence claims. At the end of the day, his guilty verdict and sentence of capital punishment were upheld. Nothing from the real facts of this case have led me to believe in Mr. Williams’ innocence, as such, Mr. Williams’ punishment will be carried out as ordered by the Supreme Court.”

During Monday’s hearing, Williams’ attorney, Jonathan Potts, claimed a prosecutor during his trial struck a juror from the jury pool “in part because he was a young Black man with glasses.”

“There was a racial component to this,” Potts said.

But the Missouri Attorney General’s office disputed that notion, saying the trial prosecutor’s intent for striking the potential juror was not due to race.

In a statement after the decision Monday, Tricia Rojo Bushnell, an attorney for Williams, said the “courts must step in to prevent this irreparable injustice.”

“Missouri is poised to execute an innocent man, an outcome that calls into question the legitimacy of the entire criminal justice system,” she said.

In his own statement Monday, Bell said he and other advocates will continue the fight to save Williams’ life.

“Even for those who disagree on the death penalty, when there is a shadow of a doubt of any defendant’s guilt, the irreversible punishment of execution should not be an option,” Bell said.

Previous attempts to halt the execution

On September 18, less than a week before the scheduled execution, Williams’ team filed a clemency petition to the US Supreme Court.

In the petition, Williams’ lawyers argued his due process rights were denied during the yearslong legal battle to save his life.

They noted that former Missouri Gov. Eric Greitens previously halted Williams’ execution indefinitely and formed a board to investigate his case and determine whether he should be granted clemency.

“The Board investigated Williams’ case for the next six years — until Governor Michael Parson abruptly terminated the process,” the lawyers wrote.

When Parson took office he dissolved the board and revoked Williams’ stay of execution, the petition noted. Parson’s decision denied Williams his right to due process, Williams’ lawyers argued.

“The Governor’s actions have violated Williams’ constitutional rights and created an exceptionally urgent need for the Court’s attention,” the court documents state.

Then, just one day before the scheduled execution, Williams’ team also asked the US Supreme Court to stay the execution based on what they say is evidence of racial bias in jury selection.

The case pitted Bell, who assumed the office in 2018 and now is running for Congress as a Democrat, against Republican state Attorney General Andrew Bailey, who is seeking reelection. Bailey had fought Bell’s January motion, saying new DNA test results indicated the evidence would not exonerate Williams.

Last month, Bell’s office announced it had reached an agreement with Williams. Under the consent judgment, approved by the court and Gayle’s family, the inmate would have entered an Alford plea of guilty to first-degree murder and be resentenced to life in prison.

But the state Attorney General’s office opposed the deal and appealed to the state Supreme Court, which blocked the agreement.

CNN’s Dakin Andone and Lauren Mascarenhas contributed to this report.