Texas Statutes - Section 19.02: MURDER
(a) In this section:
(1) "Adequate cause" means cause that would commonly produce a degree of anger, rage, resentment, or terror in a person of ordinary temper, sufficient to render the mind incapable of cool reflection.
(2) "Sudden passion" means passion directly caused by and arising out of provocation by the individual killed or another acting with the person killed which passion arises at the time of the offense and is not solely the result of former provocation.
(b) A person commits an offense if he:
(1) intentionally or knowingly causes the death of an individual;
(2) intends to cause serious bodily injury and commits an act clearly dangerous to human life that causes the death of an individual; or
(3) commits or attempts to commit a felony, other than manslaughter, and in the course of and in furtherance of the commission or attempt, or in immediate flight from the commission or attempt, he commits or attempts to commit an act clearly dangerous to human life that causes the death of an individual.
(c) Except as provided by Subsection (d), an offense under this section is a felony of the first degree.
(d) At the punishment stage of a trial, the defendant may raise the issue as to whether he caused the death under the immediate influence of sudden passion arising from an adequate cause. If the defendant proves the issue in the affirmative by a preponderance of the evidence, the offense is a felony of the second degree.