By her own telling, Mississippi authorities provided Carolyn Bryant Donham with preferential treatment rather than prosecution after her encounter with Emmett Till led to the lynching of the Black teenager in the summer of 1955. Instead of arresting Donham on a warrant that accused her of kidnapping days after Till’s abduction, an officer passed along word that relatives would take her and her two young sons away from home amid a rising furor over the case, Donham said in a 2008 memoir made public last month. The sheriff would later claim Donham, 21 at the time, could not be located...