In criminal cases husband and wife shall be allowed, and, subject to the rules of evidence governing other witnesses, may be compelled to testify in behalf of each other, but neither shall be compelled, nor, without the consent of the other, allowed to be called as a witness against the other except in the case of a prosecution for an offense committed by one against the other, or against the child, father, mother, sister or brother of either of them. The failure of either husband or wife to testify, however, shall create no presumption against the accused, nor be the subject of any comment before the court or jury by anyone.