Neuropsychology's role in capital mitigation

Neurolaw is a newly emerging area of law that looks at the brain and behavior in legal situations. In Cullen v. Pinholster, the U.S. Supreme Court will consider whether the defense counsel was ineffective in presenting mitigating evidence during the penalty phase of a capital trial for robbery and multiple murders.

In the penalty phase of a capital trial, the prosecution presents aggravating evidence indicating a death sentence is appropriate, and the defense presents mitigating evidence indicating a death sentence is not appropriate. The defense’s evidence could include information that humanizes defendants and provides a context for their behaviors. Scott Pinholster’s counsel hired a psychiatrist who concluded the defendant had antisocial personality disorder, was not cognitively impaired and did not have any brain damage. The psychiatrist did not testify during the penalty phase of the trial, and no other psychological opinions were sought. However, information that the defense counsel did not present at trial indicated that Pinholster had suffered several traumatic brain injuries and that he had a long history of mental health institutionalization, impulsive acts of violence and psycho-social issues. Pinholster’s mother was the only mitigating witness for the defense, and she provided little mitigating information. The prosecution presented ample evidence of aggravating factors, and Pinholster was sentenced to death. One of the questions before the court is whether counsel was ineffective because he failed to investigate brain damage evidence more thoroughly than merely consulting with a psychiatrist and the defendant’s mother; and whether relief for the penalty phase of the trial is therefore warranted. The appeals court determined that Pinholster’s counsel was ineffective because he did not reasonably investigate factors such as Pinholster’s abusive childhood, his mental health and the effect of his brain injuries on his behavior. They also found that there was a reasonable likelihood that the sentence would have been life but for this error.

This case raises two questions that psychological research could illuminate: What would be reasonable attorney behavior in this case and would presenting information on brain injury have altered the sentence?

One of the crucial questions for attorneys is deciding when and what type of mental health witnesses should be used, especially when defendants possibly have a brain injury that might affect their decision-making. In this case, there was substantial evidence of history of brain injury, but no witness testified about how this could have affected the defendant. There is extensive research linking neuropsychological functional impairment to increased likelihood of impulsive behavior, poor decision-making and violence. Specifically, damage to areas of prefrontal cortex, ventromedial frontal regions, and temporal lobe areas have been linked to increased aggression and poor problem-solving abilities. Recent Supreme Court cases (Atkins v. Virginia; Roper v. Simmons) have ended capital punishment for mentally retarded and juvenile defendants. These rulings are grounded in part on the relationship among cognitive impairment, brain development and violence, and reflect a belief that diminished capacity decreases moral culpability. Although most capital defendants will not meet the criteria for mental retardation, many have low verbal IQs and deficits in executive functioning and memory. In these cases, it may be reasonable during the penalty phase for a forensic neuropsychologist to explain the defendants’ level of cognitive functioning and how these deficits may have impacted their ability to regulate behavior.

Would presenting neuropsychological evidence have changed the outcome of this case? Although it is assumed that neuropsychological data would have placed the defendant’s violent behavior in some type of context, research in this area is lacking. Neuropsychological information may be used as a powerful mitigator, but the effect of this type of information may also hurt the defendant. For example, brain injuries linked to increased aggression and violence may decrease perceptions of culpability but increase perceptions of dangerousness.

The field of neurolaw would benefit from a better understanding of the pros and cons of presenting neuropsychological data during capital cases. Research on the impact of neuropsychology in mitigation may help courts determine if this type of testimony would change the outcome of cases and whether counsel’s failure to provide it is unreasonable. Overall, much psychological research is needed to assist courts with these decisions.

“Judicial Notebook” is a project of APA’s Div. 9 (Society for the Psychological Study of Social Issues).