The Missouri Supreme Court and Gov. Mike Parson have declined to halt Tuesday’s execution of a death row inmate prosecutors say may be innocent, leaving his fate in the hands of the US Supreme Court with less than 24 hours to go before he is scheduled to die by lethal injection.

Lawyers for Marcellus Williams, who maintains his innocence, argued Monday the execution should be halted over the exclusion of a potential Black juror.

Missouri Gov. Mike Parson, a Republican, on Monday rejected Williams’ clemency request to spare him from the death penalty and instead sentence him to life in prison. Parson, a former sheriff, has been in office for 11 executions, and has never granted clemency.