Self-Defense vs. Defense of Others
A detailed comparison of these two criminal law rules, including key differences, exam strategies, and guidance on when to apply each.
Overview
Self-defense and defense of others are both justification defenses in criminal law that permit the use of force, including potentially deadly force, under certain circumstances. They share the same core principles but differ in the perspective from which the threat is evaluated and the historical limitations on who may invoke the defense.
Self-defense allows a person to use reasonable force to protect themselves against an imminent threat of unlawful force. The defendant must have a reasonable belief that force is necessary, must use proportional force (deadly force only against a threat of death or serious bodily harm), and in most jurisdictions cannot be the initial aggressor. The duty to retreat varies by jurisdiction: a minority of states require retreat before using deadly force if retreat can be accomplished safely (except in the home under the castle doctrine), while the majority follows stand-your-ground principles allowing the use of force without retreating.
Defense of others extends the self-defense privilege to the protection of third parties. Under the modern majority rule, a defendant may use reasonable force to protect another person if they reasonably believe that the third party is facing an imminent threat of unlawful force. The old "alter ego" or "shoes of the other" rule, which required the third party to actually have been entitled to use self-defense, has been largely abandoned. Under the modern approach, an honest and reasonable mistake about the third party's right to self-defense does not forfeit the defense. The force used must still be proportional to the perceived threat.
Key Differences
| Aspect | Self-Defense | Defense of Others |
|---|---|---|
| Who is protected | The defendant themselves | A third party |
| Perspective for threat assessment | Defendant's reasonable belief about threat to themselves | Defendant's reasonable belief about threat to the third party (modern rule) |
| Historical limitation | No special limitation based on others' rights | Old alter ego rule: third party must actually have right to self-defense (largely abandoned) |
| Relationship requirement | No relationship required; inherent right | Modern rule: no special relationship required (anyone can defend anyone) |
| Retreat requirement | Varies: duty to retreat in minority jurisdictions, no duty in stand-your-ground states | Generally follows the same retreat rules as self-defense |
Exam Tips
On a criminal law exam, self-defense and defense of others typically appear together. Analyze self-defense first for the person being threatened, then defense of others for anyone who intervenes. The key issues are: (1) Was the threat imminent? (2) Was the belief in the threat reasonable? (3) Was the force proportional? (4) Was the defendant the initial aggressor? For defense of others, note whether the jurisdiction follows the modern reasonable belief standard or the old alter ego rule. The modern rule is more forgiving of mistakes. Also remember that the right to use deadly force is limited to situations involving a threat of death or serious bodily harm under both defenses.
When to Apply Which
Apply self-defense when the defendant used force to protect themselves from a perceived threat. Apply defense of others when the defendant used force to protect a third party. Both require the same proportionality and reasonableness analysis. The main difference is the perspective: self-defense evaluates the defendant's perception of threat to themselves, while defense of others evaluates the defendant's perception of threat to another person.