The execution of a man who killed three people out of fear they would tell police about his methamphetamine dealing has been delayed.
John Middleton was scheduled to die at one minute after midnight for the deaths in rural northern Missouri in 1995.
With less than two hours to go until the execution, US District Judge Catherine Perry granted a stay, deciding there was enough evidence of mental illness that a hearing should take place.
It will not now take place until midday on Wednesday at the earliest.
Courts have previously established that executing the mentally ill is unconstitutional.
Missouri Attorney General Chris Koster appealed to the 8th US Circuit Court of Appeals, which adjourned for the night without making a ruling.
If the stay is lifted, the state could execute the 54-year-old at any time on Wednesday.
Only Texas and Florida have performed more executions than Missouri this year, with seven each.
The death warrant expires at midnight on Thursday, meaning the Missouri Supreme Court would have to set a new date for Middleton’s execution if there is no decision.
The case could eventually end up at the US Supreme Court.
Middleton was convicted of killing Randy “Happy” Hamilton, Stacey Hodge and Alfred Pinegar because he was concerned they would tell police about his methamphetamine dealing.
His girlfriend, Maggie Hodges, is serving life in prison after pleading guilty to second-degree murder in all three cases.
Middleton’s attorneys say the wrong man was arrested, citing new evidence that includes a witness who came forward in February.
Attorney Joseph Perkovich said: “We’re looking at a situation where if (Middleton) had zealous representation at trial he likely would have been acquitted.”
Mr Koster disagreed, writing in a court response: “The time for enforcement of Missouri’s criminal judgment against John Middleton is long overdue.”
Middleton was a meth dealer in sparsely-populated northern Missouri in the 1990s.
After several drug suspects were arrested on June 10, 1995, he allegedly told a friend: “The snitches around here are going to start going down.”
The next day, according to court records, Middleton and Hodges met Mr Hamilton and Ms Hodge on a gravel road.
Prosecutors say Middleton then shot and killed the pair and put their bodies in the boot of Hamilton’s car.
Pinegar, another meth dealer, was shot in the face on June 23, 1995 and his body was found in a field near the city of Bethany.
Middleton, who allegedly told acquaintances about his crimes, was charged with all three killings and convicted in 1997.