Self-defense justifies conduct that would otherwise be a crime, because the defendant used force to fend off an unlawful attack. It is a justification rather than an excuse, which means the law treats the act as rightful, not merely forgivable. The defendant must have believed force was necessary, that belief must have been reasonable, and the amount of force must have been proportionate to the threat.
Elements
- An unlawful threat. The force being resisted must itself be unlawful.
- Imminence. The threatened harm must be immediate, not a danger expected at some future time.
- Necessity and proportion. Force must be necessary, and deadly force is permitted only against a threat of death or serious bodily harm.
- Reasonable belief. The defendant must actually believe force is needed, and that belief must be reasonable. A genuine but unreasonable belief may reduce murder to manslaughter under an imperfect self-defense doctrine.
- Retreat. A minority of states require retreat before deadly force where it can be done in complete safety. The castle doctrine excuses retreat in the home.
- The initial aggressor. Generally cannot claim the defense unless the aggressor withdrew and communicated that, or the victim escalated to deadly force.
Leading cases
- People v. Goetz: New York's standard was objective, so the jury had to ask whether a reasonable person in the defendant's situation would have believed deadly force was necessary, not simply whether the defendant believed it.
- State v. Norman: a battered woman who killed her sleeping husband could not have the defense submitted to the jury, because the threat was not imminent on the court's reading of that requirement.
- State v. Abbott: in a retreat jurisdiction, the duty applies only to deadly force and only where retreat can be made with complete safety.
Where students go wrong
The first mistake is treating the belief as purely subjective. Almost every jurisdiction requires the belief to be reasonable, and the fight is over how much of the defendant's own situation goes into that assessment.
The second is skipping imminence. It is the requirement that decides the hardest cases, including many involving long-term abuse, and it must be addressed head on rather than folded into necessity.
The third is confusing justification with excuse. Self-defense says the act was right. Duress and insanity say the actor is not to blame. That difference affects accomplices and the availability of resistance.
FAQ
Is there a duty to retreat?
It depends on the state. Most impose no duty. A minority require retreat before using deadly force where it is completely safe to do so, and the castle doctrine lifts that duty in the home.
What is imperfect self-defense?
A doctrine in some states under which a defendant who honestly but unreasonably believed deadly force was necessary is guilty of manslaughter rather than murder.
Can the person who started a fight claim self-defense?
Usually not, unless the aggressor clearly withdrew and communicated that withdrawal, or the other party responded with deadly force to a non-deadly attack.
Related terms
Working through this in your own casebook takes longer than reading it here. Syllume starts from your syllabus and turns each assigned case into a brief you can study from.