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FILE - In this 2007 file photo provided by the Missouri Department of Corrections is John Middleton. Middleton is scheduled to die for the 1995 murder of Alfred Pinegar, a suspected drug snitch in rural Missouri. (AP Photo/Missouri Department of Corrections, File)

BONNE TERRE, Mo. (AP) — The U.S. Supreme Court has refused a last-minute request to halt a Missouri execution, leaving few options for convicted killer John Middleton.

Middleton is scheduled to die Wednesday for killing three people in remote northern Missouri in 1995.

After the Supreme Court denied Middleton's earlier requests for a stay, his attorneys filed another petition. The court also denied that request.

And Missouri Gov. Jay Nixon has denied a request for clemency.

The execution was originally scheduled for 12:01 a.m. but has been delayed all day by legal wrangling.

Missouri law allows a 24-hour window for executions. That means if Middleton has not been executed by midnight Thursday, the Missouri Supreme Court would need to set a new execution date.