On November 29, 1963, President Lyndon Johnson directed the Warren Commission to “evaluate all the facts” in the brutal November 22 murder of his predecessor, John F. Kennedy, on a downtown Dallas street in broad daylight. Reduced to its bare essentials, the investigation sought answers to three fundamental questions: Who, why and how? “Why” was entirely contingent on “who,” and that depended on “how.” Thus, the linchpin of the Warren Report—and every subsequent investigation—has always been precisely how Kennedy was assassinated in Dealey Plaza. That is the finding from which all the important answers flow; mishandle that question and the...