---
title: "Defense of Others"
type: Legal Rule
source: https://casebriefly.com/legal-rules/defense-of-others
---

# Defense of Others

Defense of others allows a person to use reasonable force to protect a third party from imminent unlawful harm. The defender may use the same level of force the third party would be entitled to use in self-defense.

## Definition

Defense of others is a justification defense that permits a person to use force to protect a third party from what the defender reasonably believes to be an imminent threat of unlawful physical harm. The doctrine extends the right of self-defense beyond the individual, allowing intervention on behalf of others who face danger. Like self-defense, it results in a complete acquittal if successfully established.

Historically, the common law limited this defense through the "alter ego" rule, which allowed a defender to step into the shoes of the person being protected and exercise only the rights that person would have had. Under this restrictive approach, if the third party was actually the aggressor or had no right to self-defense, the defender who intervened would have no defense regardless of how reasonable their perception of the situation appeared. The modern trend, adopted by the Model Penal Code and most jurisdictions, has abandoned the alter ego rule in favor of a reasonable belief standard.

Under the modern approach, the defender is justified in using force if a reasonable person in the defender's position would have believed the third party was in imminent danger of unlawful harm. The defender may use the level of force that would be justified if the third party were exercising self-defense, including deadly force when the third party faces a threat of death or serious bodily injury. The defender must also satisfy proportionality requirements and may not use excessive force. The defense applies regardless of the relationship between the defender and the third party; a stranger may intervene to protect another stranger.

## Elements

- Reasonable belief that the third party is facing imminent unlawful physical harm
- The force used must be proportional to the threat facing the third party
- Deadly force is justified only when the third party faces death or serious bodily harm
- Under the modern rule, the defender's reasonable belief governs, not the third party's actual right to self-defense
- No special relationship between the defender and the third party is required

## Key Case

People v. Young, 11 N.Y.2d 274 (1962)

## Landmark Cases

| Name | Citation | Significance |
| --- | --- | --- |
| People v. Young | 11 N.Y.2d 274 (1962) | Applied the alter ego rule, holding that a defender who intervened against plainclothes officers had no defense because the arrested person had no right to resist |
| State v. Beeley | 653 A.2d 722 (R.I. 1995) | Applied the modern reasonable belief standard, allowing defense of others based on the defender's reasonable perception of the situation |
| Commonwealth v. Martin | 369 Mass. 640 (1976) | Recognized that the defense of others doctrine applies with the same scope as self-defense under the reasonable belief standard |

## Exam Tips

- Determine whether the jurisdiction follows the alter ego rule or the modern reasonable belief standard; the outcome can differ dramatically
- Apply the same proportionality analysis as self-defense: the defender can use the level of force the third party would be entitled to use
- Watch for fact patterns where the apparent victim is actually the aggressor; under the alter ego rule, the defender loses the defense

## Common Mistakes

- Assuming the alter ego rule still applies everywhere; the modern trend overwhelmingly favors the reasonable belief standard
- Forgetting that the defender must still satisfy proportionality requirements; excessive force is not justified even in defense of others
- Confusing defense of others with citizen's arrest; defense of others addresses immediate threats, while citizen's arrest involves apprehension after a crime

## Mnemonic Or Memory Aid

"Step in their shoes (modern: your shoes)" -- under the old rule you step into the victim's shoes; under the modern rule, what matters is what you reasonably believed

## Related Rules

- self-defense
- castle-doctrine
- necessity-defense

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Source: [Defense of Others — CaseBriefly](https://casebriefly.com/legal-rules/defense-of-others)