Unfortunately, once a conviction is final, it's fairly hard for courts to use any sort of discretion; there are strict limits, made stricter by legislation in recent years, on what kinds of challenges they can consider. Though as the article notes, the exact scope of the limits as applied here is unclear, so they might conceivably be expanded.

On the other hand, executive pardons and commutations have always been intended as a partial safety valve against too process-focused jurisprudence: the idea is that a thoughtful executive has the power to say, "this is not the just outcome" in specific cases, approving exceptions outside of the usual proceedings of the law. Unfortunately for that theory, though, in the past few decades pardons and commutations have become a big political risk. If you pardon someone, you get no major benefit (a handful of bleeding-heart liberals will like you, but not many), unless the person is really well-connected. But, you incur a bit potential risk if the person you pardoned ends up committing a future crime; the "Willie Horton problem". So the safe course of action is to let ten innocent people rot in jail, rather than risk pardoning a dangerous person (the exact opposite of the traditional maxim).