Unless otherwise limited by the ensuing provisions of this article defining justifiable use of physical force, conduct which would otherwise constitute an offense is justifiable and not criminal when: 1. Such conduct is required or authorized by law or by a judicial decree, or is performed by a public servant in the reasonable exercise of his official powers, duties or functions; or 2. Such conduct is necessary as an emergency measure to avoid an imminent public or private injury which is about to
1. When the commission of an offense defined in this chapter, or some element of an offense, requires a particular culpable mental state, such mental state is ordinarily designated in the statute defining the offense by use of the terms "intentionally," "knowingly," "recklessly" or "criminal negligence," or by use of terms, such as "with intent to defraud" and "knowing it to be false," describing a specific kind of intent or knowledge. When one and only one of such terms appears in a statute defining