Criminal Law

Criminal Law Defenses: Self-Defense

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You have the right to protect yourself from physical harm. If someone attacks you, you can act in self-defense without being liable for a crime. But what’s self-defense really? Is it punching someone who threatens you? Is it using force only after retreating as much as humanly possible?

Much of the law on self-defense is the same throughout the country. The law is consistent in that you may use force—even deadly force when appropriate—for self-protection. But the precise circumstances in which you may legally use force, and the amount of force you may legally use, vary somewhat from place to place.

This article takes a look at the essence of self-defense law. For more detail on the topic, including the issues of “aggressors,” “stand your ground” as opposed to the duty to retreat, and the “castle doctrine,” see our article on limits to self-defense.

Self-Defense Overview

At its core, the doctrine of self-defense applies when someone:

  • isn't the aggressor
  • reasonably believes force is necessary for self-protection against imminent and illegal violence, and
  • uses a proportional amount of force.

Self-defense can be boiled down to three basic components:

  • necessity
  • proportionality, and
  • reasonable belief.


Self-defense doesn’t allow people to use force simply because they think it’s justified. Rather, it allows them to use it when it’s necessary.

Imminent harm. The threat of harm must typically be happening or about to happen. So, if Vic yells at Dom, “I’m going to come back here and beat you up some day,” Dom can’t punch him in the face.

Deadly force not necessary. The law sometimes permits the use of deadly force when there’s a deadly threat, but not when nondeadly force would be enough. For instance, if little Vance raises a crowbar as if to strike hulking Darron on the head, and Darron knows or should know that he can stop Vance without killing him, he can’t kill Vance in self-defense.

Duty to retreat. In some states, but not all, you may not use deadly force against an aggressor if you know that you can safely retreat.


To act in self-defense, force must not only be necessary—the amount of force must be appropriate for the occasion. You couldn’t, for example, use fatal force to stop a nondeadly attack. Suppose Valerie aims to slap Darcy; Darcy can’t retrieve a revolver from her waistband and shoot Valerie.

Reasonable Belief

The self-defense doctrine applies when you reasonably believe that the force you use is necessary. If you believe that you need to kill someone, but a reasonable person in the same situation wouldn’t have believed as much, then self-defense doesn’t apply. (But, depending on the law, the partial defense called “imperfect” self-defense, which reduces murder to manslaughter, could be available to someone in this position.) On the other hand, if you reasonably believed that your force was necessary for self-preservation, you have a self-defense claim even if you were mistaken.

Suppose Victoria, minding her own business, sees Danny point what she perceives to be a gun at her. In reality, it’s a water pistol. Not knowing that it's a water gun, and there being nowhere she can safely retreat, she grabs her own gun and fires at Danny. If a jury determines that the water pistol looked like a real firearm and that Victoria’s mistaken belief was reasonable, she’s entitled to an acquittal.

Questions for Your Attorney

  • What, exactly, is the applicable law on self-defense in my case?
  • How “imminent” must a threat be in order to use self-defense?
  • Who decides whether I acted in self-defense?
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This article was verified by:
John D. (Jack) Arseneault | May 26, 2015
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