The Supreme Court is going to hear the case of Metrish v. Lancaster, concerning a Michigan man (Burt Lancaster, believe it or not) who shot and killed his girlfriend in 1993. He asserted defenses of insanity and diminished capacity during trial, but was convicted. But due to an error made during jury selection, his conviction was overturned on appeal, and the state retried him in 2005.
Between his first and second trials, the state of Michigan abolished the diminished capacity defense, which Lancaster intended to use again. And again he was convicted, perhaps in part because he could not make a claim of diminished capacity.
So he has appealed this second conviction, claiming the denial of his opportunity to use the diminished capacity defense violated his due process rights. Since it was a legitimate defense at the time of his act, and was a settled part of Michigan common law at that time, he cannot be denied the opportunity to make that claim.
In response the State of Michigan claims the diminished capacity defense was never authorized statutorily, and was never a settled part of Michigan common law. Therefore he has no right to the defense and he has suffered no denial of due process.
A very technical case, to be sure, but an important one for due process–can the state change the rules of the game on you in mid-course (not that they were intending to change the rules on Mr. Lancaster, but that’s the effective result). I don’t know enough of that area of constitutional law to make much of an argument for either one side or the other. Note that even if he wins, that doesn’t mean Michigan can’t eliminate the diminished capacity defense, just that this law can apply only to crimes that happened after its elimination. But as precedent it’s broader than that because it could apply to other changes in criminal procedure that occur between the time of some crime’s commission and the defendant’s trial.
On such obscure technical details does the course of justice turn. And that’s why you should always get an attorney.