A federal judge has ordered FBI experts to construct three bombs similar to the one allegedly planted at the Martin Luther King Jr. Day Unity March on Jan. 17, as preparations continue for suspect Kevin W. Harpham’s Sept. 12 trial. Agents already tested three devices at FBI headquarters in Quantico, Va., but Harpham’s lawyers were not informed until afterward. Defense expert Jerry Taylor, a retired Bureau of Alcohol, Tobacco, Firearms and Explosives agent, is to observe the new detonations, and the FBI is to build up to three additional devices to detonate at his request, U.S District Court Judge Justin Quackenbush said.