Section 118

All persons shall be competent to testify unless the court considers that they are prevented from understanding the questions put to them or from giving rational answers to those questions by tender years, extreme old age, disease, whether of body or mind, or any other cause of the same kind.

Explanation — A mentally disordered person or a lunatic is not incompetent to testify unless he is prevented by his condition from understanding the questions put to him and giving rational answers to them.

Dumb witnesses.