Introductory note: Grouped within this chapter are a number of affirmative defenses (that is, defenses as to which, generally, the defendant must bear the burden of proof) that will allow the defendant to escape conviction, even though the prosecution may be able to prove all the elements of the crime. These defenses are: (1) duress; (2) necessity; (3) self-defense; (4) defense of others; (5) defense of property; (6) law enforcement (arrest, prevention of crime and escape); (7) consent; (8) maintenance of authority; and (9) entrapment. While the underlying rationale varies somewhat from defense to defense, there are two recurring reasons for exculpating the defendant: (1) because his conduct was a choice of the lesser of two evils; and (2) because his conduct, even if not a choice of the lesser of two evils, was all that a person of ordinary firmness or courage would do in the situation.