Part I of this article will examine the current state of the insanity defense in Tennessee and the most common issues that arise when it is litigated. Part II of this article will provide a general overview of the present version of the insanity defense, looking at its background, the procedural prerequisites for raising it, and its elements. Part III will examine the burden of proof for the insanity defense. Part IV will discuss the scope of expert testimony with respect to the insanity defense. Part V will examine what happens after the insanity defense has been litigated at trial, looking at the appellate standard of review and the procedure upon a verdict of not guilty by reason of insanity. Part VI will briefly examine some issues related to the insanity defense such as “diminished capacity,” sentencing, and post-conviction claims.