Justification is a defense raised where a defendant admits to committing the crime but states that circumstances justified their actions (Schmalleger et. al, 2010). This defense places focus on the character of the behavior in the circumstances. Essentially, it supposes conduct otherwise criminal to be legally acceptable and avert punishment. In simple terms, the defendant shows that in the circumstances they had no choice but to do the act which they have been called to answer to.
On the other hand, excuse is a defense raised where the defendant acknowledges committing the crime but states that they had no criminal intent thus they are not criminally liable. The lack of criminal intent or mens rea, is based on the fact that either the defendant could not legally have it or it was negated by circumstances. It may be also that the actions were involuntary thus again lacking the requisite criminal intent. This defense places focus on the moral culpability of the defendant. Examples of excuses include: insanity; automatism; age; diminished capacity; intoxication and mistake.
The main difference between these two defenses is that under justification, the criminal conduct is approved under the circumstances while under the excuse defense the criminal conduct is not approved but a reason is adduced to negative criminal liability. Another major difference is that excuses focus on the moral culpability while justifications focus on the nature of the conduct in the situation.
Examples of defenses that may serve as justifications are entrapment, defense of others, use of lawful force, duress, self defense, consent, necessity and defense of habitation and property. It is however worth noting that some of these defenses do not apply or may not be accepted in certain states. Additionally, some of them for instance entrapment may be subject to certain tests before they can be successfully raised.
Schmalleger, F., Hall, D. E. & Dolatowski, J. J. (2010). Criminal law today (4th ed.).
Upper Saddle River, NJ: Pearson Learning. Print.