(1) In any legal proceeding where a child of tender years is offered as a witness, and such child does not, in the opinion of the judge, or other presiding officer, understand the nature of an oath, the evidence of such child may be received, though not given upon oath, if, in the opinion of the judge, justice or other presiding officer, as the case may be, such child is possessed of sufficient intelligence to justify the reception of the evidence, and understands the duty of speaking the truth.