Burr was charged with treason for assembling an armed force to take New Orleans and separate the Western from the Atlantic states. He was also charged with high misdemeanor for sending a military expedition against territories belonging to Spain. George Hay, the prosecuting U.S. Attorney, compiled a list of over 140 witnesses, one of whom was Andrew Jackson. To encourage witnesses to cooperate with the prosecution, Thomas Jefferson gave Hay blank pardons containing Jefferson's signature and the discretion to issue them to all but "the grossest offenders"; Jefferson later amended these instructions to include even those the prosecution believed to be most culpable, if that meant the difference in convicting Burr.