Tex. Penal Code § 37.05: RETRACTION.

It is a defense to prosecution under Section 37.03 (Aggravated Perjury) that the actor retracted his false statement:

(1) before completion of the testimony at the official proceeding; and

(2) before it became manifest that the falsity of the statement would be exposed.

Acts 1973, 63rd Leg., p. 883, ch. 399, Sec. 1, eff. Jan. 1, 1974. Amended by Acts 1993, 73rd Leg., ch. 900, Sec. 1.01, eff. Sept. 1, 1994.