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ST. LOUIS (AP) _ The Missouri Supreme Court has refused to halt the execution of deputy sheriff’s killer over claims that he is mentally incompetent.

The court issued the 4-3 ruling on Saturday in the case of 74-year-old Cecil Clayton. He is scheduled to be executed Tuesday for the 1996 shooting death of Barry County deputy Christopher Castetter. The father of three was 29 in 1996 when he went to Clayton’s home near Cassville to check on a suspicious vehicle report. Authorities said Clayton shot the deputy once in the head even before he got out of his car.

Clayton’s claim of mental incompetence stems from a brain injury suffered in a sawmill accident in 1972. The dissenting opinion noted that the injury led to the loss of 20 percent of his frontal lobe.