Trial court’s improper restriction on defendant’s use of psychiatric testimony regarding his post-traumatic stress disorder (PTSD) requires reversal of murder conviction. A jury convicted defendant of first degree murder and found that he personally used a knife (Pen. Code, §§ 187, subd. (a), 12022, sub. (b)(1)). During trial he claimed that PTSD, stemming from repeated sexual abuse he suffered as a child, caused him to fear that the deceased, who was a long-time friend, was going to molest him, and he reacted violently. The court restricted the evidence from defendant’s forensic psychologist, holding the defense expert could not testify about “anything related to mental state at the time . . . of the offense.” On appeal defendant claimed this ruling denied him a fair trial and the right to present a defense. Held: Reversed. Penal Code sections 28 and 29 limit the nature of testimony experts may provide in criminal cases. Evidence regarding mental disorder used to negate a defendant’s capacity to form any mental state is prohibited, but may be offered on the issue of whether defendant actually formed a required specific intent, premeditated, deliberated, or harbored malice aforethought (Pen. Code, § 28). An expert may not opine whether a defendant had or did not have the required mental states for the charged crime (Pen. Code, § 29), but may testify regarding the defendant’s mental state at the time of the offense. The trial court abused its discretion in refusing to permit the defense expert to testify regarding defendant’s particular diagnoses and mental condition and their effect on him at the time of the homicide.

The error was prejudicial because defendant admitted killing the deceased. The only trial issue was defendant’s mental state at the time of the homicide. The trial court’s evidentiary ruling vitiated the claim that defendant had lapsed into a dissociated stated in which he did not deliberately premeditate the stabbing. It also precluded the jury from effectively evaluating the doctor’s testimony regarding defendant’s PTSD and its relation to the issues of self-defense, imperfect self-defense, and heat of passion.

The full opinion is available on the court’s website here: http://www.courts.ca.gov/opinions/documents/B261842.PDF