(c) jurors: Provided that where the witness is a child under twelve years of age, and the Court or person having authority to examine such witness is of opinion that, though he understands the duty of speaking the truth, he does not understand the nature of an oath or affirmation, the foregoing provisions of this section and the provisions of section 6 shall not apply to such witness, but in any such case the absence of an oath or affirmation shall not render inadmissible any evidence given by such witness nor affect the obligation of the witness to state the truth. Nothing herein contained shall render it lawful to administer, in a criminal proceeding, an oath or affirmation to the accused person, or necessary to administer to the official interpreter of any Court, after he has entered on the execution of the duties of his office, an oath or affirmation that he will faithfully discharge those duties.