The historians Nancy Isenberg and Andrew Burstein write that Burr "was not guilty of treason, nor was he ever convicted, because there was no evidence, not one credible piece of testimony, and the star witness for the prosecution had to admit that he had doctored a letter implicating Burr." In contrast, lawyer and author David O. Stewart concludes that Burr's intention included "acts that constituted the crime of treason, but that in the context of 1806, "the moral verdict is less clear." He points out that neither invasion of Spanish lands nor secession of American territory was considered treasonous by most Americans at the time, in view of the fluid boundaries of the American Southwest at that time, combined with the widespread expectation (shared by President Jefferson) that the United States might well divide into two nations.