For those who find Souter overinclined to meddle in a state's punishment scheme, as judged by his Marsh dissent, today's majority opinion in Clark v. Arizona ought to be heartening. It allows states to depart from the traditional M’Naghten insanity test (of which I first heard in A Time to Kill), so a paranoid schizophrenic who killed a cop can use a psychologist's evaluation to defend himself as insane, but if it does not convince the jury of his legal insanity, he cannot use it to point to a diminished mental capacity incompatible with the necessary mens rea for first-degree murder of a police officer. Roberts, Scalia, Thomas and Alito joined the opinion in full, and I get the impression that its 39 pages might have been shortened had it been written by one of them; Souter seemed to be trying to pick up additional votes with the care and length he put into it. Breyer agreed that M'Naghten was not the constitutionally required standard, but was concerned that state law will not be applied the way Souter thinks it is being applied, and therefore wanted to remand to the Arizona Court of Appeals to clarify that it would be, rather than affirm and assume the best. (Prof. Kerr is thus not exactly right in saying that Breyer joined Souter's opinion.)
Stevens and Ginsburg joined Kennedy's dissent, which has an almost Scalian tone of annoyance with the majority, despite its self-description as "this respectful dissent":
Clark claims that the trial court erred in refusing to consider evidence of his chronic paranoid schizophrenia in deciding whether he possessed the knowledge or intent required for first-degree murder. Seizing upon a theory invented here by the Court itself, the Court narrows Clark’s claim so he cannot raise the point everyone else thought was involved in the case. The Court says the only issue before us is whether there is a right to introduce mental-disease evidence or capacity evidence, not a right to introduce observation evidence. This restructured evidentiary universe, with no convincing authority to support it, is unworkable on its own terms. Even were that not so, however, the Court’s tripartite structure is something not addressed by the state trial court, the state appellate court, counsel on either side in those proceedings, or the briefs the parties filed with us. The Court refuses to consider the key part of Clark’s claim because his counsel did not predict the Court’s own invention. It is unrealistic, and most unfair, to hold that Clark’s counsel erred in failing to anticipate so novel an approach. If the Court is to insist on its approach, at a minimum the case should be remanded to determine whether Clark is bound by his counsel’s purported waiver.Kennedy is not content with Breyer's caution as to whether Arizona law is what Souter thinks it is; he is instead quite convinced that Souter misunderstood it.
In some respects, I'm leery of moving away from actual insanity as one's defense against a crime. The misbegotten result "guilty but mentally ill" too often allows juries to relieve their feelings about the vileness of a crime by convicting the offender, while simultaneously acknowledging the clear inability of the convicted to appreciate what she was doing. This seems to have been what occurred in the original Andrea Yates trial. However, I don't think this is a danger in Clark's case; he wants to use evidence of his mental illness to show that he lacked the mens rea requisite for killing a police officer, which is a more grievous crime than killing someone else. Clark is not denying that he killed, only that he knew he was killing (insanity defense) and especially that he knew whom he was killing (regular-murderer-not-a-cop-killer defense).