Missouri corrections officers drenched an inmate with pepper spray and ignored his pleas for help for four hours, responding only when his screaming stopped as he died in the Tipton Correctional Center, a federal lawsuit filed this month alleges.

A death row inmate in Missouri who has long claimed his innocence and is scheduled to be executed in less than one week asked the US Supreme Court on Wednesday for a stay of execution, arguing his due process rights were denied during the yearslong legal battle to save his life.

The St. Louis County Prosecuting Attorney’s Office will appeal to the Missouri Supreme Court a judge’s ruling upholding the conviction and death sentence for Marcellus Williams, whose execution is one week away.