Mens Rea and PTSD
August 22nd, 2016

People v. Herrera (2016) 247 CA4th 467 held that exclusion of psychiatric testimony regarding the defendant’s post-traumatic stress disorder (PTSD) required reversal of his murder conviction. PC 28 and 29 limit the use of mental disorder evidence 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 (PC 28). Thus, an expert may not testify that the defendant had or did not have the required mental states for the charged crime (PC  29). However, the expert may permissibly testify regarding the defendant’s mental state at the time of the offense. Hence, the judge in Herrera erred by 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.

Moreover, 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.


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