A teenager accused of killing his stepfather with a samurai sword denied it Thursday but testified that the retired police officer had molested him for years and had threatened to kill him if he told anyone. Zachary Gibian, 19, said that he came home the morning of the slaying in 2005 to find his mother covered in blood and his stepfather dead in the living room with a huge gash in his neck. The teenager claimed that Scott Nager had repeatedly forced him to perform a sex act on him, sometimes with a pistol held to his head, beginning when he was about 15. "He'd laugh at me and tell me I had no rule over him," Gibian said. "If I ever told on him he would kill me and my mother. He told me no one would believe me."