(1) An oath or affirmation in the prescribed manner shall be administered to every member of every court-martial and to the Judge advocate before the commencement of the trial.
     (2) Every person giving evidence before a court-martial shall be examined after being duly sworn or affirmed in the prescribed form.
     (3) The provisions of sub-section (2) shall not apply where the witness is a child under twelve years of age and the court-martial is of opinion that though the witness understands the duty of speaking the truth, he does not understand the nature of an oath or affirmation.