G.R. No. L-7929 March 19, 1910
Facts: Because of the many bad elements happening at Fort McKinley, Ah Chong, a cook, locked himself in his room by placing a chair against the door. After having gone to bed, he was awakened by someone trying to open the door of his room. He called out twice, Who is there, but received no answer. Fearing that the intruder was a robber, he leaped from his bed and called out again, If you enter the room I will kill you. But at the precise moment, he was struck by the chair and believing that he was being attacked, he seized a kitchen knife and struck and fatally wounded the intruder who turned out to be his roommate.
Issue: Whether or not Ah Chong was guilty of murder.
Under Article 11 paragraph 1 of the Revised Penal Code provides that to justify the act, there should be:
Unlawful aggression on the part of the person killed;
Reasonable necessity of the means employed to prevent or repel it;
Lack of sufficient provocation on the part of the person defending himself. Ah Chong was not held liable for the death of his roommate. The Supreme Court reversed the lower courts conviction of homicide, saying that Ah Chong committed a mistake of fact. He would not have stabbed his roommate had he known the identity of the person who entered the room. If the person who opened the door had really been a robber instead of his roommate, he would not be criminally liable if he had stabbed that person in self-defense.