No person shall be convicted of false swearing if he retracts his false statement in the course of the same proceeding in which it was made, if in fact he does so before it becomes manifest that the falsification is or will be exposed and before the falsification substantially affects the proceeding. Statements made in separate hearings at separate stages of the same trial, administrative, or other official proceeding shall be treated as if made in the course of the same proceeding. (Ord. 1145-85 § 67, 1985.)