Criminal Law Defenses: A Systematic Analysis

93 Pages Posted: 7 Feb 2005

See all articles by Paul H. Robinson

Paul H. Robinson

University of Pennsylvania Carey Law School


Unlike many aspects of the criminal law, defenses have not yet been the subject of comprehensive conceptual analysis. The general nature and scope of most defenses have been perpetuated for centuries with little or no question. Current debates commonly focus on whether a particular defense should apply in a particular circumstance, but rarely consider the larger perspective. How do circumstances covered by one defense compare with those of other defenses? Do defenses overlap? If so, will the outcome in identical situations vary with the defense asserted? Should it? Are there gaps between defenses, that is, circumstances in which our common sense of justice suggests that the defendant should be exculpated, yet where no defense applies? Do defenses based on theoretically analogous grounds of exculpation generate analogous results? The general inquiry, which seems never to have been undertaken, is: how does the collection of recognized defenses operate as a system?

In sharp contrast to this neglect of defenses, the American criminal law community has examined in detail the full range of offenses and their interrelation. Led by the drafters of the Model Penal Code, states have during the past two decades adopted modern criminal codes that replace a confusing and inconsistent collection of offenses with a thoughtfully organized system. The jumble of offenses in older codes was commonly drafted ad hoc, in response to one highly publicized incident or one anti-crime crusade after another. Modern codes, in contrast, define and arrange all offenses according to a single definitional scheme based on the central elements of the offense: the nature of the interest injured, the extent of the injury, and the culpability of the offender. The result is a significant consolidation of related offenses, few overlaps, few gaps, and a consistency in the organization of offenses that permits the comparisons and classifications necessary for a fair sentencing system.

There are, no doubt, many people who believe that defenses defy such systemization. Defenses, it might be argued, are the embodiment of such complex human notions of fairness and morality, tempered by the demands of utility and efficiency, that they are too complex and perhaps too illogical to be reduced to an integrated, comprehensive, and internally consistent system of exculpation. This may well be true, but the complexity and perhaps irrationality of human judgments have not deterred us in other instances, especially in the law, from attempting to devise a principled system that attempts to approximate such judgments. Advances in the behavioral sciences have repeatedly demonstrated that some systemization of human thought is possible, even though it may have absolute limits. While we may not be able to reduce our feelings about exculpation to a precise final form, the level of sophistication in examining, understanding, and setting down the most fundamental principles seems to have fallen far behind our attempts to explicate our notions of justice in other legal areas, including criminal justice matters such as offense definition and procedural fairness.

This Article attempts to provide some measure of conceptual organization for criminal law defenses that may foster a more refined system of defenses analogous to the system of offenses and offense definition embodied in most modern criminal codes. Part I of the Article describes a general conceptual framework for such a system; part II discusses the practical implications of the framework.

Keywords: Criminal law, defense

JEL Classification: K14

Suggested Citation

Robinson, Paul H., Criminal Law Defenses: A Systematic Analysis. Available at SSRN:

Paul H. Robinson (Contact Author)

University of Pennsylvania Carey Law School ( email )

3501 Sansom Street
Philadelphia, PA 19104
United States

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