Incompetency of witnesses generally

(1) A witness is incompetent to give evidence if, in the opinion of the judge, he is prevented by extreme youth, disease affecting his mind, or any other cause of the same kind, from recollecting the matter on which he is to testify, from understanding the questions put to him, from giving rational answers to those questions, or from knowing that he ought to speak the truth. (2) A witness unable to speak or hear is not incompetent, but may give his evidence by writing or by signs, or in any other manner in which he can make it intelligible, but the writing must be written and the signs made in open court, and evidence so given is deemed to be oral evidence.