Rules on Evidence
Section 50. Opinion of ordinary witnesses. - The opinion of a witness for which proper basis is given, may be received in evidence regarding -
(a) the identity of a person about whom he has adequate knowledge;
(b) A handwriting with which he has sufficient familiarity; and
(c) The mental sanity of a person with whom he is sufficiently acquainted.
The witness may also testify on his impressions of the emotion, behavior, condition or appearance of a person. (44a)
8. Character Evidence