What conditions justify defense of a third person?

• A. Use of force is justified to protect a third person when the actor could have used force had the action been directed at him
• B. Use of force is never justified to defend a third person
• C. The actor must obtain approval from law enforcement before intervening
• D. The third person must be a family member

Answer: (A)

Defense of others works the same way as self-defense: you may use reasonable force to prevent imminent unlawful harm to another person if you reasonably believe it’s necessary and you would be entitled to defend yourself in the same situation. The statement that the actor could have used force if the action were directed at him captures this privilege exactly—your right to intervene is derived from the right you have to protect yourself in the face of a threat to someone else.

In practice, this means intervening to stop an attack on another person is justified when there’s an imminent risk of harm and the force used is reasonable and proportionate to that threat. You don’t need police permission to act, and the protection isn’t limited to family members—neighbors, strangers, anyone under unlawful threat can be defended if the standard is met.

If the risk isn’t imminent, or the force used is excessive, or you wouldn’t be justified in defending yourself in the same situation, the defense wouldn’t apply.