Vanderbilt Law Review

First Page



The concept of diminished capacity allows a defendant in a criminal case to prove, usually by presenting psychiatrists who testify that he suffered from an abnormal mental condition, that he was unable to entertain the particular mens rea required for conviction.' Although courts historically have been reluctant to admit such testimony, in recent years a growing number of jurisdictions have recognized the concept of diminished capacity. Recent decisions in Pennsylvania, the District of Columbia, and North Carolina, as well as recently adopted statutes in ten other jurisdictions,illustrate the evidentiary, social, and constitutional issues raised by the concept of diminished capacity. Evidentiary problems arise as the courts evaluate the relevance and probative value of psychiatric testimony presented to negate mens rea. Social problems must be considered as the courts determine the future disposition of defendants acquitted because their mental defect prevented them from entertaining a required mens rea. Constitutional problems of due process arise in those states that require a defendant to bear the burden of proving his insanity, but refuse to allow him to demonstrate his inability to entertain a mens rea that is held to be an essential element of a crime. The purpose of this Recent Development is to analyze these decisions and statutes and to propose an approach to the concept of diminished capacity through which courts and legislatures may consider carefully all three types of issues raised by the concept and thus properly assess the benefits and detriments of admitting psychiatric testimony on the issue of mens rea.