Alexander Hamilton, whom Burr then killed in a duel. Burr fled to the West and hatched a scheme to invade Spanish territory. His motive for this bizarre scheme is still not known, but Burr was arrested for unknown reasons and tried for treason. John Marshall ruled that the Court must follow the very strict criteria the Constitution requires for a conviction of treason, and Burr went free. Marshall's precedent made it difficult for later presidents to use the charge of treason as a political tool.