Limits of Self-Defense

What is self-defense?

Self-defense is an exonerating cause of criminal liability set out in Article 20.4 of the Spanish Penal Code. It applies in cases where a punishable act is committed in order to prevent or repel an unlawful attack against a person or their rights, whether their own or another’s. Article 20.4 establishes the requirements that must be met for self-defense to apply:

1. Unlawful aggression: According to Supreme Court case law, unlawful aggression is understood as any imminent, real, direct, unjust, unprovoked, and unforeseen attack—thus intentional. It must be effective and directed against legally protected interests, such as life and physical integrity. The inclusion of honor as a protected interest remains debated.
2. Proportionality in the means used: The defense must be rational, meaning adequate to prevent or repel the attack. The person attacked cannot resort to any other option but to defend themselves against the aggressor, and the defensive action must be proportional and suitable, avoiding excessive force.
3. Absence of sufficient provocation by the defender: The Supreme Court defines sufficient provocation as that which would reasonably justify an aggressive reaction. According to doctrine, it is the kind of provocation that would cause an average person to react aggressively. Self-defense cannot be claimed if the defender provoked the aggressor into acting unlawfully.

Applying the self-defense exemption leads to acquittal. In other words, it justifies otherwise unlawful conduct, exonerating the person who acted in defense, provided there was prior unlawful aggression. Depending on the circumstances, this exemption may be complete, incomplete, or applied as an analogical mitigating factor.

Analysis by the Court

The justification for self-defense lies in two needs: the individual protection of legal interests and the defense of the law against unjust aggression. This dual foundation requires strict conditions for self-defense to apply.

The first condition, a fundamental prerequisite, is the existence of unlawful aggression by a third party, without the defender having played an active role in creating it. The aggression must be current, unlawful, and sufficiently intense to endanger or harm the protected legal interest. It must be such that it cannot be stopped by any means other than a rational defensive action by the victim or a third party. Self-defense cannot be justified if the aggressor’s intent to cause harm has not yet been outwardly expressed.

The second essential element is the rational necessity of the means used. This refers to the suitability of the chosen defensive measure—whether it was the least harmful available option and capable of ending the aggression quickly and safely. The necessity must be evaluated objectively, based on social experience and the concrete situation. The law does not require the victim or defender to take unnecessary risks or rely on less dangerous means if their effectiveness is doubtful.

This situational assessment, as highlighted in Supreme Court Judgment 268/2023 of 19 April, must be made from an objective ex-ante perspective—that is, from the point of view of what a reasonable person in the same situation would have done, taking into account the intensity of the attack, the aggressor’s danger, and the means available.

While necessity is conceptually independent from proportionality between the harm caused and the harm prevented, the constitutional and conventional basis of self-defense requires stricter scrutiny where the defensive action causes death or serious injury. This is especially relevant in cases of minor or insignificant aggression, where defensive action may not be legally justified.

Conclusion

Supreme Court Judgment 3370/2024 of 4 July strengthens the interpretation and application of self-defense as an exonerating cause of criminal liability, setting precise criteria for its assessment.

For self-defense to apply, the following must be strictly proven:

• The existence of unlawful aggression that is imminent, real, and unlawful.
• The use of rational means to prevent or repel it.
• The absence of sufficient provocation by the defender.

These elements must be evaluated objectively, from the standpoint of what a reasonable person in the same situation would have done.

This ensures that self-defense is not applied arbitrarily but in line with principles of justice and proportionality—especially where life or serious injury is at stake. The ruling not only clarifies the scope of self-defense but also provides clear guidance for its correct application, balancing the protection of rights with respect for the law.