Responsibility and Control

campaign was remarkably successful, affecting most notably the laws governing insanity and addiction.13 The trend in insanity law had been to excuse both those who suffered from an absence of rationality-a cognitive defect-and those who suffered from a lack of control-a volitional defect.Starting in the 1980s, roughly at the time of the assassination attempt on the life of Ronald Reagan, the momentum began to go in the other direction.For example, where federal courts generally had adopted the Model Penal Code's ("M.P.C.") approach recognizing both cognitive and volitional defects, 14 in 1984 Congress imposed a new insanity defense by statute, one recognizing only cognitive or rationality defects.1 5 Many states made similar changes; jurisdictions that still had something like the old M'Naghten cognitive test simply kept the law they had.By my survey, thirty states, in 1980, had two-prong insanity rules, with both cognitive and volitional prongs: only eighteen still had the older one-prong test.16 13.For the changes in the insanity defense, see RICHARD J. BONNIE ET AL., A CASE STUDY IN THE INSANITY DEFENSE: THE TRIAL OF JOHN W. HINCKLEY, JR. 121-37 (2d ed.2000).14. Section 4.01 of the M.P.C. states: "A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity either to appreciate the criminality [wrongfulness] of his conduct or to conform his conduct to the requirements of law."MODEL PENAL CODE § 4.01 (1962) (alteration in original).The first part, involving the capacity to appreciate, is the cognitive branch; the second part, involving the capacity to control, is the volitional branch.15.The statute states: It is an affirmative defense to a prosecution under any Federal statute that, at the time of the commission of the acts constituting the offense, the defendant, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of his acts.18 U.S.C. § 17(a) (1992).This statute differs from the M.P.C. defense primarily in dropping the volitional branch of that defense.But it also introduces the word "severe" before "mental disease or defect."Compare id with MODEL PENAL CODE § 4.01 (1962).16.States with a two-prong test in 1980 include: Alabama, Parsons v. State, 2 So.854 (Ala.1887); Alaska, ALASKA STAT.§ 12.45.083(a)(1972); Arkansas, ARK.