(1) Except as provided in subsection (2), a petition for the relief referred to in 46-21-101 may be filed at any time within 1 year of the date that the conviction becomes final. A conviction becomes final for purposes of this chapter:
(a) when the time for appeal to the Montana supreme court expires;
(b) if an appeal is taken to the Montana supreme court, when the time for petitioning the United States supreme court for review expires; or
(c) if review is sought in the United States supreme court, on the date that that court issues its final order in the case.
(2) A claim that alleges the existence of newly discovered evidence that, if proved and viewed in light of the evidence as a whole would establish that the petitioner did not engage in the criminal conduct for which the petitioner was convicted, may be raised in a petition filed within 1 year of the date on which the conviction becomes final or the date on which the petitioner discovers, or reasonably should have discovered, the existence of the evidence, whichever is later.