Criminal Law

One of the scientists involved in the project observed that “impartial legal decision-making may not be fundamentally different from the reasoning used in deciding to punish those who have harmed us personally.”

Revelations from ground-breaking research into the neural mechanics of decision makers will have an untold impact on criminal justice theory and policy. The law is replete with value laden principles and assumptions that might have to be reconsidered in light of how thought processes actually work.

Meanwhile, there are many practical and well-established applications of neuroimaging techniques that can have a profound effect on issues being litigated today.³

Several years ago, the U.S. Supreme Court in Roper v. Simmons⁴ concluded that juveniles did not merit the death penalty because, among other reasons, their brains were not as developed as adults. The justices relied on scientific and sociological studies brought to their attention by the respondents and amici (notably national medical and psychological associations) in their filings.

Those briefs cited neurological research based on the use of brain scanning technology. The respondent’s pointed out: “Overall, the more detailed and precise picture of brain development obtained through MRI studies provides compelling evidence that the maturation of the frontal lobes – the part of the brain that is critical for competent decision-making, control of emotions, and moral judgment – is not complete at least until age 18.”⁵

Roper presents one way in which a study of the living brain has impacted criminal defense work and our understanding of the fundamental principles and policies underlying the justice system. Neuroimaging analysis has been successfully used in other areas, such as competency assessments, mitigation arguments and in negating specific intent.

In 1978, the U.S. Court of Appeals for the Ninth Circuit reversed Morse Erskine’s conviction for knowingly making false statements with the intent to influence the actions of a federally insured bank, i.e., making a loan.⁶ The trial court had precluded his personal physician from testifying. The defense wanted to introduce evidence that he did not have the mental capacity to formulate the specific intent required for this offense (18 U.S.C. §1014). His witness would have testified that a neuroimaging scan revealed a brain defect preventing Erskine from knowing what he was doing.

The appeals court recognized that this evidence was relevant to showing that the defendant did not have specific intent or appreciate the connection between the information he gave the bank and the loan he received.

Capital Case

In another cast, defendant Henry Marshall had been abused and beaten during his formative years. The effect of these experiences on his brain and his ability to make decisions became critical to his defense when he was charged with the shooting death of a pub owner in Washington state.⁷ Against the advice of defense counsel, Marshall pleaded guilty. Later the prosecutor sought the death penalty.

The trial judge decided that Marshall was competent to enter a change of plea to guilty. Later, his new defense counsel moved to withdraw the plea assailing the competency finding.

Without holding a statutorily mandated hearing to assess his mental capacity, the court received defense expert evidence about defendant’s condition. Among the three witnesses was a neurologist who performed an MRI and found brain atrophy and abnormalities that likely existed before Marshall changed his plea to guilty. Based on the court’s colloquy with defendant at the plea hearing and testimony from a prosecution expert, the judge determined that Marshall was impaired but rational enough to have entered his plea.

During the penalty phase, the same neurologist testified for the defense. She described three tests that approached brain function from different angles:

Nonetheless, the jury sentenced Marshall to death.

Vacillating on waiving his right to appeal, a hearing was finally held to decide whether Marshall was competent to forgo his appellate rights. This time the trial judge concluded that the defendant was not competent to make the decision – although confronted with the same evidence it had reviewed at the plea hearing.

On appeal the Washington Supreme Court vacated the guilty plea on account of the lower court’s failure to either allow Marshall to withdraw his plea or order a formal competency hearing. And the power of the MRI study, along with other psychiatric evidence, was vital although not consistently interpreted by the trial court.

Alcoholism Defense

The judge in Willie Jones’ murder case denied his attorney’s request for an order to conduct neurological tests based on evidence that his client suffered from traumatic brain injury.⁹

At trial, the court sustained a prosecutor’s objection to defense expert testimony that this injury affected defendant’s ability to think. According to the Appellate Division, denying defendant’s application for testing was an abuse of discretion. Evidence of brain dysfunction, combined with 30 years of alcoholism, was central to Jones’ justification defense. And the experts would have helped the jurors understand his cognitive impairment – “a person’s ability to think and act purposely are matters outside the ken of the typical juror.”

The doctors would have done more that address Jones’ ability to form intent, they would have made clear he lacked the capacity to perceive risk.

Pituitary Tumor

In United States v. Sandoval-Mendoza,¹⁰ the crime was conspiring to sell methamphetamine, the defense was entrapment, the outcome would turn on the presence of a pituitary tumor.

Eduardo Sandoval-Mendoza was charged with conspiracy along with his twin brother. A friend who was also working with the government had introduced him to an undercover informant wanting to buy drugs. Years before this meeting, Eduardo had been diagnosed as having a pituitary tumor.

His condition left him depressed and fretful about his wife and five children’s future after he was gone. The informants recommended that he might sell drugs to make the money his family would need. Ultimately, he capitulated to their idea and participated in a sale.

At trial, Sandoval-Mendoza wanted to show that the government undercovers took advantage of his suggestibility and faulty reasoning. After an in camera Daubert hearing, the judge rejected his proffer of expert testimony. Only his sister and ex-wife were allowed to testify that the tumor made him suggestible and forgetful.

The medical evidence would have showed that the brain tumor directly affected his “intelligence, memory, and judgment.”

The defense had a board-certified neurologist with a specialty in neurophysiology ready to testify about the results of an MRI of Sandoval-Mendoza’s brain. It showed that he had an usually large tumor, which resulted in brain damage notwithstanding treatment. While neither of defendant’s experts could point to studies connecting this kind of damage with suggestiveness to commit crimes, it was evident that the trauma affected his reasoning and was associated with disinhibition.

The appeals court believed that the jury should have had a chance to evaluate this evidence for themselves. It would have aided their understanding of his predisposition to commit this crime and his susceptibility to inducement. Absent the expert medical evidence, his defense was “hidden” from the jury. The conviction had to be reversed.

Arachnoid Cyst

Herbert Weinstein had been charged with the strangulation killing of his wife.¹¹ In support of a mental disease or defect defense, his lawyer planned to introduce evidence of a PET scan performed after he was indicted. It revealed the existence of an arachnoid cyst, as well as metabolic disorders in the surrounding brain tissue. A skin conductance response (SCR) test was also performed suggesting the existence of frontal lobe lesions.

These tests formed part of the basis for the testimony being offered by defendant’s psychiatric expert. The prosecution moved to preclude any evidence based on the PET or SCR tests as scientifically unreliable. The court ordered a Frye hearing. Notably, the other bases for the expert’s opinion included MRI scans, which were not the subject of the hearing.

The judge concluded that a psychiatrist was allowed to testify relying on the “norms of the profession,” including the battery of neuropsychological tests given to Weinstein.

Weighing the Frye general acceptance standard with the statutory evidence rule permitting psychiatrists to testify in connection with mental disease and defect defenses, the court concluded: