State and federal authorities this week reopened the investigation into the 1955 murder of Emmett Till, a black teenager killed in Mississippi for whistling at a white woman. Two men dragged Till, 14, out of a relatives house at gunpoint. Fishermen later found his body in the Tallahatchie River. His mother insisted on an open casket so the world would see Tills mutilated face. The image horrified the nation and helped galvanize the civil-rights movement. Two suspects, now dead, were acquitted by an all-white jury, but a recent documentary suggested five conspirators were still alive. We owe it to Emmett Till, said Assistant Attorney General R. Alexander Acosta, to see if justice remains possible.