A federal judge cleared the way for prosecutors to use evidence seized in an illegal search in the trial of a Willowbrook man facing drug and firearm charges.In a written opinion Tuesday, U.S. District Judge Matthew F. Kennelly acknowledged law enforcement agents violated the Fourth Amendment when they conducted a warrantless search of Terry Ferguson’s home.The agents had a warrant to arrest Ferguson, but did not have a search warrant, Kennelly wrote. At the time of the search, he wrote, “an application for such a warrant …