MONTGOMERY, Ala.—An Alabama inmate whose lethal injection was halted because medical staff couldn’t find a suitable vein for the execution has died of natural causes almost four years later, his lawyer said Monday. Doyle Lee Hamm, who was convicted in the slaying of a motel clerk in 1987, died of natural causes on death row, said his longtime attorney, Bernard Harcourt. He was 64. Alabama officials postponed Hamm’s execution in February 2018 because workers couldn’t find a suitable vein to connect the intravenous line used to send lethal chemicals into his body. Hamm and the state reached an agreement the following month that prevented further execution attempts, but he remained on death row at Holman Prison because of his capital conviction, Harcourt said. Hamm suffered from an aggressive lymphatic cancer for years, Harcourt said. The Holman warden called Hamm’s brother to inform him of the prisoner’s death Sunday morning, Harcourt …