Insanity defense in Chris Kyle murder trial is about more than a medical diagnosis

As the Chris Kyle murder trial continues this week in Stephenville, Texas, it seems appropriate to open this criminal appellate blog with a brief discussion of the Texas affirmative defense of Insanity. The prosecution has already played the videotape judicial confession of Iraqi War vet Eddie Ray Routh, and it is now up to both sides’ medical experts to present evidence as to whether Mr. Routh was insane at the time he shot and killed the famous Navy SEAL Chris Kyle and his friend Chad Littlefield.

In Texas, a criminal defendant may attempt to affirmatively prove that, at the time he committed the charged conduct, he did not know that the conduct was wrong because of a “severe mental disease or defect.” The Texas Legislature has refused to define either of these terms because it’s ultimately a juror’s job, not a doctor’s, to give these terms their “common usage” meaning and to determine if the defendant is legally insane.

Expert witness testimony regarding a defendant’s mental condition at the time of the crime is NOT dispositive on the issue, at least not in this State. The Texas Court of Criminal Appeals has repeatedly held that a person can prove he was legally insane with lay witness opinion testimony alone. Because the insanity defense is based on a legal concept of knowledge of right and wrong, rather than on a strict medical definition of insanity, the Court has refused to limit a jury’s consideration of the insanity defense to a specific medical diagnosis. Otherwise, the Court has said, the issue of legal insanity would be “tried in hospitals rather than courts.”

Obviously, in a case with as high a profile as the alleged murder of Chris Kyle, both the prosecution and defense will nevertheless put on a “battle of the medical experts” in the hopes of convincing the jury of their particular theory. But look for the defense to repeatedly emphasize the lay opinion of the victim in this case, Chris Kyle himself, who, in a message that ominously foreshadowed the tragedy that was about to unfold, texted Chad Littlefiled that “This guy is nuts” while the three men were driving towards the shooting range. Under Texas statutory and case law, Mr. Kyle’s own opinion about the mental stability of Mr. Routh is entirely relevant as to whether Mr. Rough was legally insane that day.