Def atty informs me that he's going for a Not Guilty based on Diminished Capaity/Self-Defense (?!). I can't seem to wrap my brain around what appear to be such separate issues. I'm confused as to how those can be used together, and thus I cannot yet formulate a clear response. Here's my case:

CW and Def know each other and both use(d) drugs. Def is also going to claim diagnosed Bi-Polar and Depression. CW and Def get into verbal argument, escalates to physical altercation when CW takes a "welcome mat" and swings it/hits Def. Def takes out his knife and swings at CW once, stabbing him in the left ear. The stab gets CW's jugular and carotid. CW able to walk a little bit, falls down apt breezeway stairs, bleeds out. Def leaves scene, gets rid of knife (never found), goes to friend's apt down the street at different apt complex, changes shirts, says he just cut a man, and leaves again. Def ultimately turns himself him when hears police looking for him.

Talk to Kim Schaefer in your appellate division. She wrote an article about this a couple years ago. You need to read Jackson v. State, 160 S.W.3d 568 (diminished capacity concept exists in Texas) and Ruffin v. State, 270 S.W.3d 586 (it applies to offenses beyond homicide). As I understand it, testimony of his mental illness(es) will be admissible if it directly rebuts his ability to form the culpable mental state for the offense.

JohR's right about the Jackson case. As far as the self-defense claim goes, though, I have a hard time grasping how a welcome mat can be seen as deadly force, which would make deadly force immediately necessary. I'm picturing a little green mat with plastic daisies on it. Ooo! Scary!

I have long argued in instructing mental health experts (and now in assisting the courts) that diminished capacity is not an affirmative defense in Texas. I am not dissuaded from this opinion on the basis of Jackson.

It may seem subtle or insignificant, but I don't think this to be the case.

On the other hand, Jackson does state that evidence may be presented to establish that the defendant lacked the requisite state of mind at the time of the act with which charged, i.e. to negate mens rea. This however is to be distinguished from what Jackson describes as a "lesser form of the insanity defense..."

I have a bigger problem believing that a "mental health" expert is in any better position to interpret the mental state of a defendant than your average citizen. Jackson doesn't create a diminished capacity defense, but it does imply that the opinions of "experts" should carry more weight than the obvious inferences the rest of us apply.

I agree with Floyd: diminished capacity, as it is usually meant, is not a defense. Disproving the culpable mental state has always been a defense. If the evidence shows the defendant did not "intentionally or knowingly" cause the death, then it doesn't matter whether you call it diminished capacity or something else, it is simply a factual defense.

Well, John, I agree -- and the beautiful lines from Graham v. State apply, wherein the court stated that the trier of fact could accept some of an expert's opinion, all of the expert's opinion, or none of it. Experts should not usurp the functions of the court; for in any issue, the expert but assists the trier of fact....

But I question whether an expert's opinion is any more reliable than the informed opinion of a layperson. In particular, how does a mental state expert check his own work to see whether it is error-free? By what standard does a forensic psychiatrist check the accuracy, over time, of his or her opinions? Short answer: they don't.

And, without such a standard, we see trial after trial in which two experts offer opposite opinions, each saying they meet the professional standards. That is not science.

I guess my point is this: Jackson shouldn't guarantee that a mental state expert gets to testify. It only says that the evidence may be relevant. But that doesn't make it reliable enough to gain entry through Rule 705. Challenge the expert. Ask the gatekeeper to keep out unreliable expert testimony.

That's why Daubert and its prodigy have been so powerful...and why, in many states (or in federal court), the expert is not permitted to testify as to the ultimate issue.

How is the murder charged? Is it charged as he intentionally killed the victim or is it he intends to cause serious bodily injury and in doing so committed an act clearly dangerous to human life? If charged in the latter, how does his "diminished capacity" fit? I really can't see how swinging a knife at someone is not an intentional act to cause serious bodily injury or that it is not clearly dangerous to human life.

In that case, under the diminished capacity theory, the defendant would offer evidence to show that he did not intend to cause serious bodily injury, because of some mental problem that he has. In other words, he's arguing that the State's evidence fails to prove the element of intent to cause serious bodily injury. Unlike insanity, which he would have to prove and which would entitle him to an acquittal, his argument may only entitle him to a lesser offense conviction if the State cannot prove he had the requisite intent.

Your observation that a person who swings a knife at someone else must have intended to seriously injure them is the very argument the prosecutor will make to convince the jury that the defendant is guilty. The defense will argue that the defendant did swing the knife, but did not intend to cause serious injury.

The jury should recieve no special instructions on diminished capacity because it is built into the elements of the case. All the Texas courts have said about it is that a defendant is entitled to be allowed to present the evidence if it is relevant to proving or disproving the element of his mental state.

In other words the twinkie defense is alive and well.