A last-minute stay from a federal judge has put a Missouri inmate's execution temporarily on hold.

John Middleton was scheduled to die one minute after midnight Wednesday for killing three people in rural northern Missouri in 1995. With less than two hours to go before the execution, U.S. District Judge Catherine Perry granted a stay, ruling there was enough evidence of mental illness that a new hearing should be held.

Courts have established that executing the mentally ill is unconstitutional.

Missouri Attorney General Chris Koster appealed to the 8th U.S. Circuit Court of Appeals, but that court adjourned for the night without a ruling.

It was a confusing end to a day that saw a flurry of court actions. Perry first granted a stay early Tuesday, but that was overturned by the appeals court. The U.S. Supreme Court refused to overturn the appeals court ruling and declined to halt the execution on several other grounds, including the contention by Middleton's attorneys that he was innocent of the crimes.

Middleton's attorneys then went back to Perry, who once again granted a stay.

However the appeals court eventually rules, the case is likely to end up again in the U.S. Supreme Court.

If the stay is lifted, the state could execute Middleton at any time Wednesday. The death warrant expires at midnight Thursday and if Middleton is not executed by then, the Missouri Supreme Court would have to set a new date. State witnesses and media were told to report back to the prison by 10:30 a.m.

Middleton, 54, would be the sixth man put to death in Missouri this year — only Florida and Texas have performed more executions in 2014 with seven each.