Evidence must not only come from credible witness but also must be credible in itself

In the assessment of self-defense theory, the Court is guided by the now-familiar rule that "evidence to be believed, must not only proceed from the mouth of a credible witness, but must be credible in itself - such as the common experience of mankind can approve as probable under the circumstances. We have no test on the truth of human testimony, except its conformity to our knowledge, observation, and experience." Consequently, we hold that the trial court was correct in considering the scenario conjured up by the defense as completely unworthy of belief, being inconsistent with normal human conduct. Even the number and extent of the injuries sustained by the victim are inconsistent with the testimony of Virgilio Obzunar that he inflicted only one stab wound upon the victim with his knife, and his small stature vis-a-vis the big and robust victim. [G.R. No. 92153. December 16, 1996]