dissenting.
I agree with the majority that the evidence Dietz sought to introduce about his and Christine’s past physical altercations was “habit” evidence admissible under Texas Rule of Evidence 406. However, I do not believe the error in excluding the proffered testimony was of constitutional magnitude or resulted in reversible harm, therefore, I respectfully dissent.
The Court of Criminal Appeals has held that the exclusion of defensive evidence rises to the level of constitutional error if the evidence “forms such a vital portion of the case that exclusion effectively precludes the defendant from presenting a defense.” Potier v. State, 68 S.W.3d 657, 665 (Tex.Crim.App.2002). Here, the exclusion of the evidence did not preclude Dietz from presenting his defense.
At trial, the jury heard Dietz’s version of the events that led to Christine’s injuries. Dietz testified both he and Christine had been drinking during a party hosted by the couple, but that only Christine was drunk. By the time the last person left the party, Christine was passed out on a kitchen table. Dietz said he tried to call his mother before he decided to talk to Christine about her seeing another man because he wanted to get someone over there before he got “in trouble.” He said when he spoke to Christine, “When she finally opened her eyes, she came out screaming and bit me in the stomach and scratched me in the face.” At this point, he tried to call Christine’s mother, but Christine slapped the phone out of the wall. He said he grabbed her wrists and they fell to the ground. He was on top of her, trying to stop her from kicking him. He said he tried to get away from her, but could not because she continued to hit him. He said he hit his wife because she was biting his finger. After he hit her, she left *534the house and he stayed in the house until the police arrived.
Other evidence, admitted at trial, tended to support Dietz’s version of the incident. Rebecca Jones, the couple’s neighbor, was the last to leave the party. She testified to Christine’s drinking and she said Christine was passed out on the table when she left the party. Shortly after Jones returned to her own home, Christine rang her doorbell, crying and saying defendant had hit her. Jones stated that Christine said she did not know what started the fight or what had happened. Jones said it was “out of character” for defendant to be violent. Dietz’s mother said that when she arrived at the couple’s home after the incident, Christine told her she did not know what happened. In Christine’s statement to police, given two days after the incident, Christine said she did not remember how the fight started or how she got hit.
Although the erroneously excluded evidence was relevant, its exclusion did not prevent Dietz from presenting the substance of his defense. Therefore, the error was not of constitutional dimension. “Exclusions of evidence are unconstitutional only if they ‘significantly undermine fundamental elements of the accused’s defense.’ ” “That ‘[the defendant] was unable to present his case to the extent and in the form he desired is not prejudicial where, as here, he was not prevented from presenting the substance of his defense to the jury.’ ” Potier, 68 S.W.3d at 666 (citations omitted); see also Valle v. State, 109 S.W.3d 500, 506-07 (Tex.Crim.App.2003) (holding same). Because Dietz’s substantial rights have not been affected, I would affirm the trial court’s judgment. See Tex.R. Evid. 103(a); Tex.R.App. P. 44.2(b); Potier, 68 S.W.Sd at 666.