In Ruffin v. State, 270 S.W.3d 586 (Tex. Crim. App. 2008), the defendant shot at approaching police officers because, due to his delusional state, he believed the officers were Muslims who were "waiting to kill him with a knife." Id. at 590. The court concluded that the defendant's mistaken perception, caused by a mental defect, was relevant to mens rea because it proved that he did not intend to shoot at police officers. Id. at 594; see also Tex. Penal Code Ann. 22.02(b)(2)(B) (enhancing punishment for aggravated assault if assailant intentionally attacked public servant in discharge of duties). However, the court emphasized that the defendant was still guilty of aggravated assault because he intended to shoot at a person, but simply did not appreciate that the person he was shooting at was a police officer. Ruffin, 270 S.W.3d at 594. At trial, the appellant "contended that he was suffering from severe delusions and believed that he was shooting at Muslims, not police officers." Id. Defense counsel proffered testimony by Carter that, on the day of the standoff, the appellant "was suffering from psychotic symptoms such as hearing or seeing things that did not exist," "was not fully aware of the effects his behavior was having on other people," and had a "diminished capacity" to make rational judgments. Id. at 590. Carter stated that, because of mental illness and delusions, the appellant did not know that he was shooting at law-enforcement officers. Id. The trial court excluded Carter's testimony but the Texas Court of Criminal Appeals reversed, holding that the testimony is "clearly relevant to the issue of whether appellant intended to shoot at police officers during the standoff or whether, because of a mental disease and the delusions that he suffered as a result of that disease, he believed that he was shooting at Muslims or some other figment of his mind." Id. at 596. The Court noted that "affirmative defenses, other than insanity, based on mental disease, defect, or abnormality . . . do not exist in Texas." Id. at 593 ("Insanity is the only 'diminished responsibility' or 'diminished capacity' defense to criminal responsibility in Texas."). However, because "mental diseases or defects may affect a person's perception of the world," evidence of a defendant's "history of mental illness" may be considered to the extent it "directly rebuts the particular mens rea necessary for the charged offense." Id. at 588, 593, 596. In Ruffin v. State, the defendant "contended that he was suffering from severe delusions and believed that he was shooting at Muslims, not police officers." Ruffin, 270 S.W.3d at 587. The trial court excluded the testimony of a psychologist that "a person who is delusional typically believes that his delusions are true." Id. at 590. The psychologist also expressed his professional opinion that the defendant was suffering from psychotic symptoms on the day of the offense and that he "'was not fully aware of the effects his behavior was having on other people.'" Id. The Court of Criminal Appeals reasoned that the excluded evidence was "clearly relevant to the issue of whether appellant intended to shoot at police officers during the standoff or whether, because of a mental disease and the delusions that he suffered as a result of that disease, he believed that he was shooting at Muslims or some other figment of his mind." Id. at 596. The Court drew an analogy between a blind person and a person with a mental disease or defect. Ruffin, 270 S.W.3d at 593-94. The court reasoned that just as a blind person would be permitted to offer evidence that his blindness prevented him from understanding that a person he shot at was a police officer, so too could a person suffering from mental delusions offer evidence about those delusions if they prevented him from apprehending that the person he shot at was a police officer. Id. at 594. In that case, the court held that the proffered testimony that the defendant, because of a mental disease and attendant delusions, believed he was shooting at someone other than police officers was "clearly relevant." Id. at 596. In sum, in Ruffin v. State, the defendant was charged with multiple first-degree felony offenses of aggravated assault of a public servant after he fired several shots at police officers. Ruffin, 270 S.W.3d at 587. The mens rea element of the charged offenses was that appellant intended to shoot at the police officers. Id. at 594. The defendant and other lay witnesses testified that the defendant suffered from delusions. Id. at 596-97. The defendant said that he believed he was shooting at a "trespasser" and "hundreds of Muslims" instead of police officers. Id. at 590. The trial court excluded expert testimony from the defendant's psychologist relating to the existence and severity of the defendant's mental disease and delusions, and the court of appeals held that the trial court did not abuse its discretion by excluding the testimony. Id. at 587. The court of criminal appeals held that the expert testimony was relevant to rebut the mens rea element of the offense that the defendant intended to shoot at police officers. Id. at 596-97. The court explained as follows: If . . . the defendant suffers from mental delusions such that he sees a "trespasser" or a "Muslim" when everyone else around him sees a police officer, he cannot be convicted of intentionally shooting at a police officer, although he may be convicted of intentionally shooting at a trespasser or Muslim. Guilt of the greater offense requires that the State prove, beyond a reasonable doubt, that the defendant intended to shoot a police officer, not a trespasser or Muslim. Id. at 594. Thus, in Ruffin, the psychologist's testimony, if believed, would have lessened the offenses from first-degree aggravated assaults of police officers to second-degree aggravated assaults (an intentional shooting at a "trespasser" or at "Muslims"). Id. at 594.