After a string of inmate deaths in Mississippi that began late last year, the Justice Department announced Wednesday that it is opening a civil rights probe into the state's penitentiary system. The department's civil rights division says it will examine conditions at four Mississippi prisons, including the state penitentiary at Parchman, the state's oldest, where a prison riot broke out on Dec. 29 after an inmate was killed. The all-male prison includes the state's death row