It has long been the policy of American criminal law to excuse from criminal responsibility those who commit offenses while insane. In nearly every State, the insanity defense is the means by which this policy is implemented. Moreover, it is the traditional policy of American criminal law for those acquitted by reason of insanity to receive psychiatric treatment at a mental institution if the insanity manifested at the time of the crime still exists at the time of acquittal. Despite this general consensus in the law, wide differences exist among States as to the proper definition of legal insanity, the procedures which should be followed for litigating the existence of insanity, and the procedures to be followed for commitment and release of those acquitted by reason of insanity. There is a trend among the States, however, to abandon the restrictive M'Naghten test of legal insanity in favor of the broader American Law Institute test, which differs from the M'Naghten test by making a lack of substantial capacity sufficient to escape criminal responsibility, while in M'Naghten, total impairment of capacity is required. Also, some States have adopted commitment and release procedures more nearly like those provided to persons subject to civil commitment. Many fear that such changes will result in the acquittal and release of dangerous persons. These fears are providing the impetus for the enactment of laws which will permit the verdict of 'guilty but mentally ill,' which permits the imposition of a prison sentence for a person pleading not guilty by reason of insanity, with psychiatric treatment being required during the sentence. Such a verdict tends to undermine the concept of criminal responsibility as a requirement for the imposition of the sanctions attending guilt. Such a verdict is especially unnecessary in Kansas, where existing laws automatically commit acquitted insane persons to the State security hospital. A total of 271 footnotes are provided. (Author summary modified)