What Is the Ex Post Facto Clause Definition ?
Among other things, the ex post facto clause prohibits "every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed." Carmell v. Texas, 529 U.S. 513, 522, 146 L. Ed. 2d 577, 120 S. Ct. 1620 (2000)(quoting Calder v. Bull, 3 U.S. 386, 390, 1 L. Ed. 648 (1798)).
Both the United States Supreme Court and this Court have addressed the issue of prior crimes used to enhance punishment and have declined to find an ex post facto violation. McDonald v. Massachusetts, 180 U.S. 311, 45 L. Ed. 542, 21 S. Ct. 389 (1901); Shaw, 529 S.W.2d at 76.
In arriving at its holding the Supreme Court found that enhancement statutes penalize the new criminal offense being enhanced rather than the prior offense used for enhancement:
"The punishment is for the new crime only, but is the heavier if he is an habitual criminal....The statute, imposing a punishment on none but future crimes, is not ex post facto." McDonald, 180 U.S. at 313-314.