A man who murdered a sheriff 's deputy years after doctors removed part of his brain will be put to death in Missouri next week - but his lawyers are fighting for him to be saved . Cecil Clayton , from Purdy , will be executed at the state prison in Bonne Terre at 6pm on March 17 for the November 1996 shooting of Barry County Sheriff 's Deputy Christopher Castetter . But his attorneys are making a last-ditch attempt to save him by calling for a competency trial - saying a traumatic brain injury makes it impossible for him to understand his death sentence . In 1972 , 24 years before he killed the officer , Clayton was using a sawmill when a board splintered and a shard went into his head above his right eye , the St Louis Post-Dispatch reported . Facing death : Cecil Clayton is scheduled to die in Missouri next week but his lawyers are calling for a competency hearing . Twenty years before he murdered a cop , he had part of his brain removed , they say . Doctors were forced to remove 20 per cent of his frontal lobe , the area of the brain that controls decision making and emotions , the newspaper reported as it called for Clayton to be spared . Following the accident and before the arrest , Clayton frequently went to mental health facilities , spending up to 15 months at a time under psychiatric care . Then the evening before Thanksgiving in 1996 , Deputy Castetter responded to a call about a suspicious vehicle parked outside Clayton 's girlfriend 's mother 's home . Earlier that night , Clayton and his girlfriend had been arguing , and prosecutors said he then took a loaded gun to her mother 's house . Clayton walked up to the deputy 's patrol car window and shot him in the head at point-blank range . Castetter , a 29-year-old married father-of-three , died in the hospital later that day . He was convicted of the murder in October 1997 and sentenced to death later that year . His attorneys argued that he was mentally incompetent to stand trial but despite their appeals , state and federal appeals courts have upheld the conviction and the death penalty . His lawyers are now seeking a competency hearing to determine whether he understands his death penalty . Mental health professionals who have examined him agree that he is mentally impaired and has mental health issues , including dementia . 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 . His most recent IQ test found he had an IQ of just 71 - 29 points below the 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 . ' But there is no agreement on how much he understands his death penalty or his other options . 'If you can prove mental retardation , you can get exempted , but mental illness alone is not an exemption to the death penalty , ' Richard Dieter , executive director of the Death Penalty Information Center , told the New York Times . 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 concluded that Clayton is mentally ill , but could not be certain that he does n't understand his death sentence . Execution : He is scheduled to be put to death at the state prison in Bonne Terre , pictured , next Tuesday . Death : His family and lawyers are arguing that he is child-like and does not understand the significance of his death penalty . They are calling for his execution at Bonne Terre ( pictured ) to be stopped . But Clayton 's lawyers say , while he may have conversations in which he understands he is about to be executed , he will later forget that conversation ever happened . His family have also called for a fair hearing on the issue . '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 . ' Clayton , who is the state 's oldest death row inmate , will be put to death between 6pm on March 17 and 5.59pm on March 18 . He will become the second person put to death in the state in 2015 , after a record 10 executions in Missouri in 2014 . Last month , Walter Storey was put to death for slitting his neighbor 's throat 25 years ago .
Lawyers for Cecil Clayton are seeking a competency trial to halt his execution , which is scheduled for March 17 at 6pm . In 1972 , 24 years before he shot dead a police officer , he suffered a sawmill accident that caused a shard of wood to go into his head . Doctors were forced to remove 20 per cent of his frontal lobe . His lawyers argue that he has a low IQ , mental illness and is not competent enough to understand his death sentence . But a doctor from Missouri Department of Mental Health previously concluded that he did understand the punishment .