Missouri's oldest death row inmate was executed on Tuesday for murdering a sheriff's deputy, after the U.S. Supreme Court and the governor declined to spare the 74-year-old whose attorneys said he had a diminished mental capacity because of a sawmill accident decades ago. 'They brought me up here to execute me,' Cecil Clayton uttered before he was put to death by lethal injection after Governor Jay Nixon denied a clemency request. After a final meal of fried chicken, mashed potatoes, corn, green beans and a cola, he was executed at the correctional center in Bonne Terre at 9.13pm and was pronounced dead at 9.21pm. Clayton was executed despite repeated attempts by his lawyers to spare his life, claiming he had an IQ of just 71 after suffering a traumatic brain injury decades before he killed the officer in 1996. Put to his death: Cecil Clayton, 74, was executed by lethal injection at 9:13 p.m. on Tuesday for the 1996 murder of Deputy Sheriff Christopher Castetter. He was pronounced dead at 9:21 p.m. The nation's high court turned aside appeals after the Missouri Supreme Court, in a 4-3 ruling, also declined to intervene. The court's majority concluded last weekend that there was no evidence Clayton - despite his brain injury - wasn't capable of understanding his circumstances. The U.S. Supreme Court was also divided, with four judges saying they would have granted a stay. Mike O'Connell, spokesman for the Missouri Department of Corrections, said in a statement that Clayton was executed at 9.13pm and pronounced dead at 9:21 p.m. The claim of diminished mental capacity stemmed from a 1972 sawmill accident that Clayton's attorneys argued cost him about eight percent of his brain, including 20 per cent of the frontal lobe portion governing impulse control and judgment. Combined with his reported IQ of 71 and reading skills of a fourth-grader, Clayton's attorneys insisted psychiatric evaluations over the past decade concluded that the inmate didn't understand the significance of his scheduled execution or the reasons for it, making him ineligible to be put to death under state and federal law. In their 11th-hour appeals, Clayton's attorneys had argued that his deteriorating mental health left him convinced his conviction was a plot against him and that God would rescue him from a death sentence at the last minute, 'after which time he will travel the country playing the piano and preaching the gospel.' The appeals were ultimately rejected. 'Cecil Clayton had - literally - a hole in his head,' said Elizabeth Unger Carlyle, one of his attorneys, following his death on Tuesday night. 'Executing him without a hearing to determine his competency violated the Constitution, Missouri law, and basic human dignity... The world will not be a safer place because Mr. Clayton has been executed.' But the victim's family were in support of his killer being put to death. Missing: A brain scan shared by his lawyers show a significant section of his brain is missing . At a press briefing on Tuesday evening, James Castetter thanked authorities for convicting Clayton for the 'senseless murder' of his brother, Chris Castetter. 'We know this execution isn't going to bring Chris back,' he said. 'But it destroys an evil person that would otherwise be walking this earth. 'There is no doubt in my mind that Cecil knew what he had done... The Great State of Missouri did not kill an innocent man. Cecil Clayton's actions is what put him to death.' Clayton was convicted of gunning down Christopher Castetter, a sheriff's deputy in rural southwest Missouri's Barry County. Castetter was 29 and a father-of-three when he went to a home near Cassville on Thanksgiving Eve 1996 to check on a suspicious vehicle report. Authorities said Clayton shot Castetter once in the forehead while the deputy was in his car, which was found against a tree, its engine racing and wheels spinning. Clayton's brother had testified that the sawmill accident led to Clayton's breakup from his wife, alcohol abuse and violent outbursts. The lethal injection, Clayton's attorneys said, was 'sure or very likely to cause excruciating or tortuous pain and needless suffering' in light of his dementia. 'If Missouri proceeds with its scheduled execution of Mr. Clayton, it will be conducting an unregulated experiment on a human subject, as there are no studies that support (the prison system's) use of Missouri's lethal injection protocol on an individual suffering from severe brain damage,' the appeals on Clayton's behalf argued. Killed: Barry County Sheriff's Deputy Christopher Castetter, pictured left, was shot dead by Clayton, pictured right in an old mug shot, as he responded to a call about a suspicious vehicle in 1996 . At the weekend, when the Missouri Supreme Court issued its decision, three of the seven judges agreed that Clayton was entitled to a competency hearing. Mental health professionals who examined him agreed that he was mentally impaired and had mental health issues, including dementia. His most recent IQ test had found him to have an IQ of just 71, which is 29 points below average. 'He is not simply incompetent legally; he would be unable to care for himself or manage basic self-care, were he not in a structured environment that takes care of him,' according to a doctor who examined him, the Kansas City Star reported. 'He can shower, groom, eat, walk; it is his comprehension, judgment, memory, limited intelligence and social deficits that plague him.' In Missouri, the director of the Department of Corrections is the only one with the authority to order a competency hearing, and last year, he called on a doctor to examine Clayton. Dr. James Reynolds of the Missouri Department of Mental Health had concluded that Clayton was mentally ill, but could not be certain that he didn't understand his death sentence. But Clayton's lawyers said, while he had conversations in which he understood he was about to be executed, he would later forget that conversation ever happened. His family also called for a fair hearing on the issue. Execution: He was put to death at the state prison in Bonne Terre, pictured, on Tuesday night . Death: His family and lawyers had argued that he was child-like and did not understand the significance of his death penalty. They had called for his execution at Bonne Terre (pictured) to be stopped . 'He is brain-damaged, and talking with him is like talking to a child,' Clayton's daughter, Jena Clayton, said during his clemency petition, the Kansas City Star reported. 'I do not believe we are the kind of country that executes the disabled.' At the execution, Department of Corrections Director George A. Lombardi read a statement from Governor Jay Nixon, in which he praised the work of Castetter. 'Our state is safer because there are brave officers, like Deputy Castetter, who are willing to sacrifice their own safety for that of others,' he said. 'As the sentence of his murderer was carried out this evening, I ask Missourians tonight to honor Deputy Castetter, who gave his life in service to our state, and to remember him and his family in their thoughts and prayers.' The execution was Missouri's second this year after the state's record 10 in 2014. It was also the first Missouri carried out in the evening after decades of having them just after midnight.
Cecil Clayton was executed by lethal injection at 9.13pm on Tuesday for the 1996 murder of Deputy Sheriff Christopher Castetter . Last meal was fried chicken, mashed potatoes, corn, green beans and cola . An hour earlier, the U.S. Supreme Court had denied an appeal by his lawyers who claimed their client had diminished mental capacity . In 1972, 24 years before he shot dead a police officer, Clayton suffered a sawmill accident that speared a shard of wood into his head . Doctors were forced to remove 20 per cent of his frontal lobe, around eight per cent of his total brain mass . His lawyers argued that Clayton didn't understand his death sentence . A doctor from Missouri Department of Mental Health had previously concluded that he did understand the punishment .