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 NAACP is urging Missouri Governor Mike Parson to stop the scheduled execution of Marcellus Williams on Tuesday (September 24), Essence reports. Williams, now 55, was convicted in 1998 of killing former newspaper reporter Felicia Gayle.