Missouri Revised Statutes Title XXXVIII. Crimes and Punishment; Peace Officers and Public Defenders § 563.026. Justification generally

1. Unless inconsistent with other provisions of this chapter defining justifiable use of physical force, or with some other provision of law, conduct which would otherwise constitute any offense other than a class A felony or murder is justifiable and not criminal when it is necessary as an emergency measure to avoid an imminent public or private injury which is about to occur by reason of a situation occasioned or developed through no fault of the actor, and which is of such gravity that, according to ordinary standards of intelligence and morality, the desirability of avoiding the injury outweighs the desirability of avoiding the injury sought to be prevented by the statute defining the offense charged.

2. The necessity and justifiability of conduct under subsection 1 of this section may not rest upon considerations pertaining only to the morality and advisability of the statute, either in its general application or with respect to its application to a particular class of cases arising thereunder. Whenever evidence relating to the defense of justification under this section is offered, the court shall rule as a matter of law whether the claimed facts and circumstances would, if established, constitute a justification.

3. The defense of justification under this section is an affirmative defense.