John Henry scheduled for execution at 6 p.m. Wednesday

A federal appeals court has rejected a bid to delay the execution of John Ruthell Henry, who is scheduled to be executed at 6 tonight at the Florida State Prison in Raiford.

The U.S. Court of Appeals for the 11th Circuit in Atlanta issued an opinion late Tuesday, said capital cases clerk Jan Camp. Only the U.S. Supreme Court could now delay Henry's execution, Camp added.

Henry was sentenced to death for murdering his wife in Zephyrhills in 1985.

Defense attorney Baya Harrison, who filed the appeal over the weekend, has argued that Henry, 63, is mentally disabled and should not be put to death under the constitutional ban on cruel and unusual punishment.

Henry has been on death row for 27 years. He stabbed 28-year-old Patricia Roddy 20 times in 1976. He served just over seven years before being paroled in January 1983.

In December 1985, he stabbed his wife, Suzanne Henry, to death with a 5-inch paring knife after an argument. Hours later, he drove to Hillsborough County where he stabbed her 5-year-old son, Eugene Christian, with the same knife while the boy sat in his lap in a car.

Henry's scheduled execution comes in the wake of a botched procedure in April in Oklahoma. Clayton Lockett was administered drugs but soon started writhing in his restraints. Officials halted the execution, but Lockett later died of a heart attack. Oklahoma uses a three-drug cocktail in its executions, and according to published reports one of Lockett's veins exploded.

Florida also uses a three-drug combination. First, 500mg of a midazolam solution — to render the inmate unconscious — is injected, followed by a "flush" of saline. The executioner will check if Henry has lost consciousness, according to protocols written by the Florida Department of Corrections.

Once the execution team is satisfied Henry is indeed unconscious, two more drugs, vecuronium bromide and potassium chloride, will be administered. An on-hand physician will confirm the death.

Florida has executed 81 inmates since the death penalty was reinstated in 1979, according to DOC records.

Last year, seven were put to death, the most since 1984, when eight people were executed.