Overview

Under Article 11(1) of the Revised Penal Code (RPC), self-defense is a justifying circumstance. When properly established, it erases criminal liability because the act is deemed lawful. But self-defense stands on three pillars:

Unlawful aggression;
Reasonable necessity of the means employed to prevent or repel it; and
Lack of sufficient provocation on the part of the person defending himself.

Of these, unlawful aggression is indispensable. If it is missing, the claim collapses—no matter how “reasonable” the force used appears, and even if the accused did not provoke the incident.

This article explains what unlawful aggression is (and isn’t), how and when it ceases, why its absence is fatal, and what alternative doctrines may still soften liability when self-defense fails.

The Sine Qua Non: Unlawful Aggression

What counts as unlawful aggression?

Actual or material attack: A real, offensive act placing one in present danger—e.g., a knife swing, pistol pointing with a finger on the trigger, a chokehold, or a battering assault.
Imminent attack: An immediately threatening movement signalling the start of a material assault—e.g., drawing a gun and starting to aim, lunging with a bladed weapon, cocking and raising a firearm to fire.

Key ideas

There must be real peril, not a conjectured or remote possibility.
The danger must be present or immediately impending, not merely anticipated.

What is not unlawful aggression?

Mere words, insults, taunts, or threats without a simultaneous, overt act.
Future or conditional threats (“I’ll get you later”).
Equivocal gestures that do not reasonably portend an immediate attack.
Lawful acts performed within legal authority (e.g., a valid arrest), absent excessive or unnecessary force by the officer.

Special contexts

Defense of property: Unlawful aggression must still target the defender or be accompanied by actual or imminent danger to persons. Purely property-focused aggression rarely justifies deadly force unless it coincides with personal peril.
Multiple assailants / disparity in size or strength: These may sharpen perception of danger and inform reasonableness of responsive force—but they do not replace the requirement of an actual or imminent attack.
Regaining the right to self-defense: The initial aggressor may later lawfully defend himself only if he clearly desists and the other party continues or initiates aggression. Without clear desistance and new aggression from the other, a counter-blow is retaliation, not defense.

When Unlawful Aggression Ceases

Even if aggression existed at the outset, it may end, and with it ends the right to use defensive force:

Aggressor is disarmed, immobilized, or retreats;
Aggressor flees or is otherwise neutralized;
Physical control is achieved such that the threat is no longer imminent.

Force used after the danger ends is retaliation, not defense. The law justifies only what is reasonably necessary to prevent or repel the aggression—no more.

The Second and Third Requisites Still Matter—but Only After Unlawful Aggression

If unlawful aggression exists, courts then assess:

Reasonable necessity of the means: Not mathematical proportionality, but reasonableness in light of the immediacy, weaponry, number of attackers, location of wounds, opportunity to employ lesser means, and the speed of unfolding events. There is no rigid duty to retreat, but retreat or avoidance is relevant to reasonableness.
Lack of sufficient provocation: The defender’s prior conduct should not have sufficiently provoked the aggression. Minor irritation is not “sufficient provocation,” but starting the fight usually is.

However: If unlawful aggression is absent, analysis typically stops—self-defense fails outright.

Evidentiary Posture and Burdens

By invoking complete self-defense, the accused normally admits the act (e.g., the killing or injury) but claims justification. This shifts to the accused the burden of evidence to clearly and convincingly establish all three elements—especially unlawful aggression.
The prosecution still bears the burden of proof beyond reasonable doubt on the crime charged; yet if the accused fails to make a credible showing of unlawful aggression, the justification does not arise, and the factfinder need not weigh “reasonable necessity” at all.

Practical takeaways

Consistency matters: medical findings (e.g., entry/exit wounds), scene evidence, and witness accounts must cohere with a narrative of an imminent or ongoing attack.
Physical evidence often decides the point: shots to the back of a fleeing aggressor, or numerous finishing blows when the opponent is already disabled, tend to negate ongoing aggression.

Common Scenarios Where Self-Defense Fails for Lack (or Loss) of Unlawful Aggression

Threats and posture only Heated words, clenched fists, or even an aggressive stance—without an overt act—are not unlawful aggression. A pre-emptive strike here is generally unjustified.
After the aggressor disengages If the initial attacker turns to flee or has been subdued, a subsequent stabbing or shooting becomes retaliatory.
Mutual combat / agreed fight Where parties voluntarily engage, neither may claim self-defense unless there is a clear shift (one desists; the other continues). Otherwise, no party is “defending” against unlawful aggression.
Force against lawful acts Resisting a lawful arrest with violence is not defense against unlawful aggression—unless the officer uses excessive force, in which case the excess (not the arrest itself) might constitute unlawful aggression.
Defense of property divorced from personal peril Setting deadly traps or using lethal force against a non-violent trespass usually lacks the element of imminent danger to person.

Consequences When the Justifying Circumstance Fails

No complete justification: The act remains unlawful, and liability attaches for the appropriate offense (e.g., homicide, murder, physical injuries).
No incomplete self-defense (privileged mitigating) without unlawful aggression: Article 69 (privileged mitigating for incomplete justifying circumstances) generally requires that the indispensable element of the justifying circumstance be present. For self-defense, that indispensable element is unlawful aggression. If unlawful aggression is absent, you cannot invoke Article 69 on “incomplete self-defense.”

What may still mitigate?

Ordinary mitigating circumstances under Article 13, such as:
- Passion or obfuscation (if not intentionally sought and arising from lawful, adequate antecedent causes);
- Voluntary surrender;
- Immediate vindication of a grave offense (if the facts qualify);
- Analogous circumstances (e.g., a credible putative self-defense—a mistake of fact where the accused honestly, though unreasonably, believed he was under attack—can sometimes be treated as analogous).
Incomplete self-defense as ordinary (not privileged) mitigating is sometimes argued where some requisites (but not unlawful aggression) existed, but doctrine typically denies privileged mitigation absent unlawful aggression and treats such pleas, if at all, under analogous or passion/obfuscation mitigation depending on facts.

Putative Self-Defense (Mistake of Fact)

When the accused honestly but mistakenly believes he is under attack (e.g., misperceives a cellphone as a gun), the law may recognize putative self-defense. This:

Does not justify the act (because actual unlawful aggression is lacking);
May mitigate liability if the mistake is in good faith and reasonable under the circumstances (or at least sincere). Courts examine lighting, time pressure, prior threats, distance, and behavioral cues.

Practical Guidance for Litigants

For the Defense

Build the aggression narrative first: Identify the first overt act of the complainant/decedent that created present danger. Pin it to specific, observable movements.
Anchor in physical and forensic evidence: Weapon recovery, trajectory, stippling, defensive wounds, location of injuries. Show why the timing of the defensive act coincided with ongoing or imminent peril.
Show cessation boundaries: Explain why the force ended when the peril ended; if multiple blows/shots occurred, justify each within the rapid sequence.
Neutralize provocation: Demonstrate lack of sufficient provocation, or explain any desistance if your client began the fray.

For the Prosecution

Attack the indispensability: If you can show no unlawful aggression, the defense fails. Focus on who moved first, body positions, flight, and cessation.
Frame retaliation: Emphasize timing gaps, shots to the back, or post-neutralization blows to show that the aggression had ceased.
Offer alternative mitigations only where warranted**:** Passion/obfuscation, voluntary surrender, or analogous circumstances may be conceded where just but should not blur the absence of unlawful aggression.

Selected Doctrinal Touchstones (Doctrinal Summaries)

Unlawful aggression is the primus inter pares: Without it, there is no self-defense to speak of.
Words are not enough: Threats or insults do not constitute aggression absent a contemporaneous overt act.
Defense ends when danger ends: Continuing to strike a disarmed or fleeing aggressor is retaliation.
No privileged mitigation without aggression: Article 69 relief for “incomplete” self-defense typically requires unlawful aggression to be present; otherwise look to ordinary mitigating circumstances.
Putative self-defense mitigates, not justifies: A sincere, reasonable mistake of fact can lessen liability; it does not erase it.

Checklist (Bench and Bar)

Identify the very first unlawful act of the victim (not just words).
Fix the timeline: Was the defender’s responsive act contemporaneous with an actual or imminent attack?
Mark cessation: When did danger end? Did force continue past that point?
Assess means: Given the circumstances (weapons, numbers, location), were the means reasonably necessary?
Probe provocation: Did the defender instigate or provoke sufficiently? Was there desistance?
If self-defense fails, evaluate mitigating alternatives (passion/obfuscation, surrender, putative defense, analogous factors).

Bottom Line

In Philippine criminal law, unlawful aggression is the gateway to self-defense. Its presence activates the inquiry into reasonable necessity and provocation; its absence shuts the gate. Many close cases turn not on how harsh the defender’s response appeared in hindsight, but on whether an actual or imminent attack existed at the moment force was used, and whether that danger still existed when the final blow was struck. When unlawful aggression is missing, the justifying mantle falls away—leaving only such mitigating strands as the facts, fairness, and doctrine allow.