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The use of the term, "self-defense, " covers a wide array of defensive behaviors, and different actions that repel attacks may be permissible for different reasons. One important justificatory feature of some defensive behaviors is that the aggressor has rendered himself liable to defensive force by his own conduct. That is, when a culpable aggressor points a gun at a defender, and says, "I am going to kill you," the aggressor's behavior forfeits the aggressor's right against the defender's infliction of harm that is intended to repel the aggressor's attack. Because the right is forfeited, numbers do not count (the defender may kill as many culpable aggressors as he needs to), third parties may only aid the defender, and the defender does not owe the aggressor compensation for harms inflicted.

Although liability for culpable aggression seems intuitive, there are a number of questions, including whether culpability is a necessary requirement for liability; what actions the aggressor must perform; whether there must be an actual threat or whether an apparent threat is sufficient; and whether the defender must believe that his use of force is responsive to that threat.

The first part of this paper examines two prominent alternative theories of self-defense-Judith Thomson's rights-based account and Jeff McMahan's moral responsibility account. It argues that both of these theories are problematic as theories of liability and that culpability is a necessary condition of liability. The second part of the paper sketches a culpability account, ultimately arguing:

Liability to Defensive Force:


(la) The aggressor forms an intention to purposefully, knowingly, or recklessly kill the defender, the aggressor lacks a justification or excuse, and the defender must kill the aggressor to prevent being killed himself or

(lb) The aggressor purposefully, knowingly, or recklessly engages in conduct that he is aware may lead the defender to believe that (la) is true, and the aggressor lacks a justification or excuse for so doing;


(2) The aggressor is not wronged by force employed by the defender that is intended to repel the perceived attack.


Self-defense, aggression, justification, culpability, blameworthiness, wrongdoing

Publication Title

Ohio State Journal of Criminal Law

Publication Citation

9 Ohio State J. Crim. L. 669 (2012)