Jamaal Howard, 46, is scheduled to be executed by lethal injection in Texas on Wednesday for the 2000 killing of convenience store clerk Vickie Swartout.

Howard was convicted of capital murder after surveillance video showed him shooting Swartout during a robbery in Silsbee, Texas, before taking $114 and a carton of cigarettes.

His attorneys argue that Howard is intellectually disabled and therefore should not be executed, while Texas prosecutors maintain that he has not provided sufficient evidence to support the claim.

Howard has an appeal pending before the U.S. Supreme Court seeking to halt his execution, which would be the nation’s 30th execution of the year, NBC News has reported.

The execution would also be the first scheduled in the United States since Tennessee’s unsuccessful attempt to execute Christa Pike last week.