The most common conceptualization of defences among modern codes is that reflected in the organization of the American Model Penal Code summarized in Chapter 1. The Code recognizes what it calls 'Justification' defences in Article 3, such as self-defence and law enforcement authority, and in Article 4, under the heading 'Responsibility', it collects such defences as insanity and immaturity. In addition to these two defence groups, the Code provides a variety of defences, such as mistake, intoxication, duress, consent, entrapment, sprinkled among the provisions of Article 2, entitled 'General Principles of Liability'. Still others, such as time limitations, former prosecution, are included in Article 1, entitled 'Preliminary'. It is unclear what degree of conceptual similarity the Code drafters think exists among the defences they collect in Article 1 or among those they collect in Article 2. Here, then, are the three groupings of defences most typical of modern American codes: justification defences, responsibility-related defences, and other defences (related to general principles of liability and other preliminary matters). The Draft English Code also has a three-part structure, but one that ignores the justification-excuse distinction. It recognizes two groups of defences under the headings 'Incapacity and Mental Disorder' and 'Defences', and includes other defences in a variety of places in the General Part.
This Chapter argues that current conceptualizations hide important fundamental distinctions between defences and between defence groups, and that this obscuration distorts the theories and formulation of defences. This Chapter argues that better conceptualization and a more accurate reflection of how current law actually operates would instead recognize five groups of defences. Chapter 2 sketched the proposed categories: two groups in which the 'defences' are conceptually tied to the definition of specific offences--absent element defences and offence modification defences--and three groups of general defences that theoretically apply to all offences--justifications, excuses, and non-exculpatory defences. Let me briefly remind the reader of the five categories and their interrelation, then highlight the conclusions of the Chapter with regard to each of the groups.
Some doctrines that are called defences are nothing more than the absence of a required offence element. When I take your umbrella believing it to be my own, I may claim a mistake defence. Yet my defence derives