Insufficient justification (insufficient punishment) is a phenomenon under the realm of social psychology. It synthesizes theories of cognitive dissonance and internal vs. external justification. Essentially, insufficient justification is when an individual utilizes internal motivation to justify a behavior. It is most commonly seen in insufficient punishment, which is the dissonance experienced when individuals lack sufficient external justification for having resisted a desired activity or object, usually resulting in individuals' devaluing the forbidden activity or object. That is, when an individual can't come up with an external reason as to why they resisted doing something they wanted to, he or she decides to derogate the activity. Mild punishment will cause a more lasting behavioral change than severe punishment because internal justification is stronger than external justification.
Effort justification is an idea and paradigm in social psychology stemming from Leon Festinger's theory of cognitive dissonance. Effort justification is a person's tendency to attribute a value to an outcome, which they had to put effort into achieving, greater than the objective value of the outcome.
Justification and excuse are different defenses in a criminal case. Both defenses admit that the defendant committed an act proscribed by law. The proscribed act has justification if the act had positive effects that outweigh its negative effects, or is not wrong or blameworthy. The proscribed act is excused if the defendant's violation was not entirely voluntary, such as if they acted under duress or under a false belief. Martin v. Ohio (1986) established that states may make justification an affirmative defense, placing the burden of proof on defendant. Patterson v. New York (1977) established that states may make excuses, such as involving mental state, an affirmative defense, rather than part of the mens rea element the prosecution must prove beyond a reasonable doubt.