A North Texas man whom experts for both prosecutors and defense attorneys had said was intellectually disabled became the 600th person executed in Texas since 1982, put to death Thursday evening for the killing of a retired 77-year-old college professor. Edward Busby, Jr. was pronounced dead at 8:11 p.m. local time following a lethal injection at the state penitentiary in Huntsville, hours after a divided Supreme Court lifted a stay over his disability claims. The execution followed a series of