A former employee of Host International was found guilty of first-degree murder and robbery in the 1984 slaying of a night manager at a Los Angeles International Airport terminal. A Torrance Superior Court jury deliberated for only an hour before reaching the verdicts against Henry Earl Duncan, who had been charged with stabbing to death Josephine Eileen DeBaun, 28, in a cafeteria office and fleeing with about $2,000 from a company vault. Duncan, 21, was employed as a cashier at the cafeteria when the crimes occurred. The Compton man faces either the death penalty or life imprisonment without the possibility of parole. Deputy Dist. Atty. Robert Martin said that he will argue that Duncan should be put to death when the penalty phase of the trial begins today.