The burden of proof shifts to the person invoking self-defense, who, with clear andconvincing evidence, must establish all the following requisites: (1) unlawful aggression on the part of the victim, (2) reasonable necessity of the means employed to prevent or repel it, and (3) lack of sufficient provocation on the part of the person claiming self-defense. Upon failure to establish these requisites, conviction is inevitable because the accused, by setting up self-defense, admits being the author of the killing.