Tex. Code Crim. Proc. art. 38.36 : CODE OF CRIMINAL PROCEDURE — CODE OF CRIMINAL PROCEDURE — EVIDENCE IN CRIMINAL ACTIONS — Evidence In Prosecutions for Murder

(a) In all prosecutions for murder, the state or the defendant shall be permitted to offer testimony as to all relevant facts and circumstances surrounding the killing and the previous relationship existing between the accused and the deceased, together with all relevant facts and circumstances going to show the condition of the mind of the accused at the time of the offense.
(b) In a prosecution for murder, if a defendant raises as a defense a justification provided by Section 9.31, 9.32, or 9.33, Penal Code, the defendant, in order to establish the defendant's reasonable belief that use of force or deadly force was immediately necessary, shall be permitted to offer:
(1) relevant evidence that the defendant had been the victim of acts of family violence committed by the deceased, as family violence is defined by Section 71.004, Family Code; and
(2) relevant expert testimony regarding the condition of the mind of the defendant at the time of the offense, including those relevant facts and circumstances relating to family violence that are the basis of the expert's opinion.

Tex. Code Crim. Proc. § 38.36

Added by Acts 1993, 73rd Leg., ch. 900, Sec. 7.03, eff. 9/1/1994. Subsec. (b) amended by Acts 2003, 78th Leg., ch. 1276, Sec. 7.002(g), eff. 9/1/2003.