A person commits and offense if he intends to cause serious bodily injury and commits an act clearly dangerous to human life that causes the death of an individual.
Because there is no clear mens rea (i.e. culpable state of mind, such as intentionally or knowingly) required under 19.02(b)(2), Texas courts have not allowed a lesser-included instruction on the offense of Manslaughter (which required a mens rea of recklessness).
Not any more.
In Cavazos v. State, the Texas Court of Criminal Appeals held that Manslaughter is an LIO of Murder under 19.02(b)(2). While the CCA could not look to the specific elements of the offenses to come to a conclusion, it used a functional equivalence test, holding that the culpable mental state for Murder under 19.02(b)(2) is the intent to cause serious bodily injury, which can be substituted for recklessness under a Manslaughter theory.
Of course, Mr. Cavazos did not benefit from this holding, because the CCA also held that his particular case did not qualify for the LIO instruction. So while new law emerges, his conviction stands.