ABSTRACT
In the United States there is no bar to pleading defences in the alternative. General defences define the scope of claims that government allows actors to plead in order to exculpate themselves from criminal liability. Self-defence, necessity, and insanity are paradigmatic examples. Both justification and excuse defences have objective and subjective elements. A person may justifiably use force against a wrongful aggressor in order to protect her person, property, or habitation. Engaging in what would otherwise be criminal conduct is justified pursuant to necessity when engaging in the conduct is necessary to avert a more serious harm. Given that self-defence and necessity are justification defences, they negate the wrongfulness of the conduct. A person who commits a crime while she is legally insane is excused. Involuntary intoxication occurs when the defendant is not at fault for becoming intoxicated. Such mistakes regarding the existence of a defence are not relevant in American criminal law.
