The analysis is based largely on informed impressions of the New Mexico scene and draws extensively from the experience of the courts in Michigan, the first State to adopt a plea and verdict of 'guilty but mentally ill' (GBMI). The New Mexico GBMI statute states that a person who was not insane but was suffering from a 'mental illness' at the time of the charged offense may be found GBMI. Mental illness is defined as 'a substantial disorder of thought, mood or behavior which afflicted a person at the time of the commission of the offense and which impaired that person's judgment, but not the the extent that he did not know what he was doing or understand the consequences of his act or did not know that his act was wrong or could not prevent himself from committing the act.' It is likely that jurors will perceive such a plea and verdict as a compromise between acquittal on ground of insanity and a simple guilty verdict, with the jury's assumption being that the sentence will be mitigated by the GBMI verdict. However, the New Mexico statute provides no mitigation of sentence, as it states that the court can impose any sentence which could be imposed pursuant to law upon a defendant convicted of the same offense. The intent of the statute is to ensure that dangerous persons are institutionalized for precise periods as sanctions for the offenses committed while also specifying that treatment for mental illness will be provided. The statute, however, fails to mandate sufficiently the nature of the treatment to be received. It is left to the judgment of the Department of Corrections as to how much treatment or counseling will be provided to an offender found GBMI. There is no guarantee that the level of treatment for mentally ill offenders will rise beyond what is currently given. The statute may well undercut the insanity defense in New Mexico, since that defense is rarely successful in the State, but it leaves the statutory civil commitment procedures untouched and does little to reduce the possibility of improper release of dangerous persons under civil commitment. Eighty-seven footnotes are provided.