The Insanity Defense

The U.S. Supreme Court ruled last month that the U.S. Constitution’s Due Process Clause does not require states to provide criminal defendants with an insanity defense to criminal liability. (Kahler v. Kansas (Mar. 23, 2020) __U.S.__ [140 S.Ct. 1021; 206 L.Ed.2nd 312].) Under Kansas law (pursuant to a statutory amendment effective in 1995), defendants are precluded from arguing they were insane and unable to make moral judgments as an excuse for having committed a criminal act. Instead, Kansas law allows defendants to argue that due to a mental defect, they did not intend to commit the crime as an affirmative defense. One’s mental issues may also be argued by a defendant at the time of sentencing as a factor in mitigation. But under Kansas law, insanity itself does not provide a criminal defendant with a complete defense to his or her criminal culpability. In this ruling, the Supreme Court rejected the argument that the Fifth Amendment’s Due Process protections require the acquittal of any defendant who is unable to tell the difference between right and wrong because of a mental defect of some sort. Kansas’ legal theory, eliminating the commonly used defense of insanity, is constitutional, per the U.S. Supreme Court. California, of course, allows for an insanity defense, employing the so-called common law “McNaghten Rule” where a criminal defendant is entitled to an acquittal (i.e., “not guilty by reason of insanity”) if he can prove that he was insane at ....