Our criminal laws provide for instances where a person may defend himself and not be prosecuted for what would normally be a criminal action. Under Section 1, Article 11 of the Revised Penal Code of the Philippines, the following do not incur any criminal liability: 

“Anyone who acts in defense of his person or rights, provided that the following circumstances concur; 

First. Unlawful aggression. 

Second. Reasonable necessity of the means employed to prevent or repel it. 

Third. Lack of sufficient provocation on the part of the person defending himself.”

The justifying circumstance of self-defense “is an affirmative allegation that must be proven with certainty by sufficient, satisfactory and convincing evidence that excludes any vestige of criminal aggression on the part of the person invoking it.” (People v. Nacuspag, 115 SCRA 172 [1982]) Where the accused has admitted that he is the author of the death of the deceased, it is incumbent upon the appellant, in order to avoid criminal liability, to prove this justifying circumstance (self-defense) claimed by him, to the satisfaction of the court. To do so, he must rely on the strength of his own evidence, and not on the weakness of the prosecution for even if it were weak, it could not be disbelieved after the accused admitted the killing.

It is basic that for self-defense to prosper, the following requisites must concur: (1) there must be unlawful aggression by the victim; (2) that the means employed to prevent or repel such aggression were reasonable; and (3) that there was lack of sufficient provocation on the part of the person defending himself. We shal now discuss the following requisites in detail:

A. Unlawful Aggression:

Unlawful aggression presupposes an actual or imminent danger on the life or limb of a person. Mere shouting, intimidating or threatening attitude of the victim, assuming that to be true, does not constitute unlawful aggression. Real aggression presupposes an act positively strong, showing the wrongful intent of the aggressor, which is not merely a threatening or intimidating attitude, but a material attack. Examples are the pointing of a gun or the brandishing of a knife or other deadly weapon.

B. Reasonable necessity of the means employed:

Whether the means employed is reasonable or not, will depend upon the kind of weapon of the aggressor, his physical condition, character, size, and other circumstances as well as those of the person attacked and the time and place of the attack. Although a knife is more dangerous than a club, its use is reasonable if there is no other available means of defense at the disposal of the accused.

C. Lack of sufficient provocation on the part of the person defending himself:

“Sufficient” means proportionate to the damage caused by the act, and adequate to stir one to its commission. Imputing to a person the utterance of vulgar language is sufficient provocation. This element refers to the person defending himself and is essentially inseparable and co-existent with the idea of self-defense.