A judge has declared a mistrial in the case of a former youth detention center worker charged with raping a teenage boy in 1998. The decision came Wednesday after jurors said they were deadlocked in the trial of Stephen Murphy of Danvers, Massachusetts. Murphy was charged with aggravated felonious sexual assault. Murphy testified that he did not assault the teen. No decision on whether to retry the case has been made. Murphy is also scheduled for trial in April, July and October on 15 additional charges involving three other boys who were at the facility in the 1990s.