A South Carolina death row inmate scheduled to be executed later this month is urging the state Supreme Court to delay his execution to allow his lawyers to argue that his co-defendant who testified against him lied about having no plea deal in exchange for his testimony.

Freddie Eugene Owens, 46, is set to be executed on Sept. 20 for the 1997 killing of store clerk Irene Graves during a string of robberies in Greenville. Owens also killed his cellmate at the Greenville County Jail after his conviction in 1999, but before his sentencing.

In addition to the argument over the plea agreement, attorneys for Owens said in court papers filed Friday that a juror observed an electronic stun device Owens had to wear in court to assure good behavior and that a judge never addressed why he was required to wear it, according to the Associated Press.

This comes as South Carolina seeks to put Owens to death, which would mark the state's first execution in 13 years after an involuntary pause over struggles in recent years obtaining lethal injection drugs.

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Lawyers for the state have until Thursday to answer Owens' request to delay his execution while he presents new evidence to a judge and demands a new trial.

The bar is typically high to grant new trials after death row inmates exhaust all their appeals. Owens' lawyers said previous attorneys scrutinized his case carefully, but the new evidence only came up in interviews as his potential execution neared.

Co-defendant Steven Golden testified that Owens shot Graves in the head because she was unable to open the safe at the Greenville store 27 years ago.

The store had surveillance video, but it did not show the shooting clearly. Prosecutors never found the weapon used in the shooting and failed to show any scientific evidence linking Owens to the killing.

Golden told jurors at the trial in 1999 that he did not have a plea agreement with prosecutors and could still be sentenced to death or life in prison after testifying. 

However, in a sworn statement signed Aug. 22, Golden said he reached a side deal with prosecutors, an admission Owens' attorneys said might have changed the minds of jurors who believed his testimony.

"My written plea agreement said the death penalty and life without parole were still possible outcomes and there were no specific guarantees about what my sentence would be," Golden wrote in his statement. "That wasn't true. We had a verbal agreement that I would not get the death penalty or life without parole."

Golden was sentenced to 28 years in prison after pleading guilty to a lesser charge of voluntary manslaughter, court records show.

Addressing the electronic stun device Owens was wearing during trial, Owens' lawyers said courts have long required judges to explain to juries why defendants are wearing visible restraints, such as shackles, and that there must be debate by the judge balancing courtroom security versus the impact the device might have on a fair trial.

Owens' lawyers said the judge failed to do this in his trial.

Once one of the busiest states for executions, South Carolina has not carried out the death penalty since 2011 due to trouble in recent years obtaining lethal injection drugs after its supply expired because of pharmaceutical companies' concerns that they would have to disclose that they had sold the drugs to state officials. But the state legislature passed a shield law last year allowing officials to keep lethal injection drug suppliers private.

South Carolina previously used a mixture of three drugs, but will now use one drug, the sedative pentobarbital, for lethal injections in a protocol similar to that of the federal government.

Lethal injection, electrocution and the new option of a firing squad are all expected to be available for Owens' execution. Owens has until Sept. 6 to choose the method for his execution. He signed his power of attorney over to his lawyer, Emily Paavola, to make that decision for him.

If Owens does not make a decision, he would be sent to the electric chair, and he does not want to die that way, Paavola said. Lawyers for the state asked the South Carolina Supreme Court to rule if Owens' lawyer can make that decision for him.

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"Mr. Owens has a long-standing, deeply held religious conviction that physically signing the election form is taking an active role in bringing about his own death and is thus akin to suicide. Mr. Owens' Muslim faith teaches that suicide is a sin, and it is forbidden," Paavola wrote in court papers.

The state Supreme Court also said on Friday it would wait at least five weeks between executions.

The court rejected a request from lawyers for the condemned inmates to set three months between executions to relieve pressure on prison staff that could result in mistakes and give lawyers time to dedicate time exclusively to each prisoner's case.

Instead, the court promised five weeks between executions. Under state law and a timeline first issued when the justices ruled executions could restart last month, the court could issue execution orders every week on Friday if it wants. Prison officials told the state that four weeks would be acceptable.

South Carolina currently has 32 inmates on death row.

The Associated Press contributed to this report.