Sec. 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. (Rule 130, Rules of Court)

When may a non-expert witness give his opinion?

Under Section 50 of the Rules of Court, a non-expert witness may give his opinion regarding:

1. The identity of a person about whom he has adequate knowledge;

2. A handwriting with which he has sufficient familiarity; and

3. The mental sanity of a person with whom he is sufficiently acquainted.

4. The witness may also testify on his impressions of the emotion, behavior, condition or appearance of a person.


Cases:
US vs Manabat
7 Phil 209

The night was dark and there was no light in the house and the only mode by which the witness was able to identify the accused was by the sound of his voice. It was shown that she and the accused had known each other intimately since their youth, having lived in the same barrio for many years, so that there was nothing unreasonable in her assertion that she recognized the accused by his voice, although she could not see his face on account of the darkness.


People vs Preciados
G.R. No. 122934. January 5, 2001

The identification of an accused through his voice is acceptable, particularly if the witness knows the accused personally.


People vs Duranan
G.R. Nos. 134074-75. January 16, 2001

Accused-appellant contends that he cannot be convicted of rape since the victim’s mental age was not proven.  He argues that under the Revised Penal Code, an essential element for the prosecution for rape of a mental retardate is a psychiatric evaluation of the complainant’s mental age to determine if her mental age is under twelve. He further claims that only in cases where the retardation is apparent due to the presence of physical deformities symptomatic of mental retardation can the mental evaluation be waived.

The contention has no merit.

The opinion of a witness for which proper basis is given may be received in evidence regarding the mental sanity of a person with whom he is sufficiently acquainted.

The mother of an offended party in a case of rape, though not a psychiatrist, if she knows the physical and mental condition of the party, how she was born, what she is suffering from, and what her attainments are, is competent to testify on the matter.

It is competent for the ordinary witness to give his opinion as to the sanity or mental condition of a person, provided the witness has had sufficient opportunity to observe the speech, manner, habits, and conduct of the person in question.  Generally, it is required that the witness details the factors and reasons upon which he bases his opinion before he can testify as to what it is. As the Supreme Court of Vermont said:  “A non-expert witness may give his opinion as to the sanity or insanity of another, when based upon conversations or dealings which he has had with such person, or upon his appearance, or upon any fact bearing upon his mental condition, with the witness’ own knowledge and observation, he having first testified to such conversations, dealings, appearance or other observed facts, as the basis for his opinion.