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Should Brain Scan Data Be Used in the Courtroom?

When neuroscience data belongs in the courtroom.

Key points

  • Brain scan data should be admitted into courtroom trials when criminal responsibility is being considered as a defense.

Our American legal system presumes that people have the capacity to control their conduct and have a choice over how they act and that they are innocent until proven guilty. Therefore, when a crime is committed and the courts are tasked with deciding guilt or innocence, it makes perfect sense that all relevant evidence regarding their conduct, motive, and behaviors be examined in the courtroom in determining an outcome.

In the nineteenth century, the McNaghten rule was created in reaction to the acquittal of Daniel McNaghten on the charge of murder. He shot Edward Drummond, the prime minister’s secretary, after mistakenly identifying him as the Prime Minister of the UK, who was his intended target. Medical experts were brought in for the murder trial. They testified that he was psychotic and delusional, and he was found not guilty by reason of insanity. The defendant did not know the nature of his actions and had been too deranged to realize they were wrong.

The verdict caused an uproar from the public who had never heard of an insanity defense.

The House of Lords ordered the courts to draw up a strict definition of criminal insanity that could be used in future criminal trials. The panel stated; "Every man is to be presumed to be sane, and ... that to establish a defense on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was laboring under such a defect of reason, from disease of mind, and not to know the nature and quality of the act he was doing; or if he did know it, that he did not know he was doing what was wrong."

The American Law Institute (ALI) is a research and advocacy group of judges and legal scholars established to promote the clarification and simplification of United States common law. The ALI test further elaborates that criminal responsibility means that an individual is not responsible for criminal behavior if, at the time of the criminal act, mental disease or defect left the individual unable to know that what they were doing was illegal and they were unable to conform their conduct to the requirements of the law.

Elements of criminal responsibility are determined by each state complicating the construct further.

Herbert Weinstein stood indicted for the crime of murder in the second degree. The indictment alleged that Weinstein murdered his second wife, Barbara, on January 7, 1991. Weinstein allegedly strangled her in their 12th-floor apartment in Manhattan, and then threw her body from a window to make her death appear to be a suicide.

Weinstein's attorney had filed notice that the defense at trial will be that Weinstein lacked criminal responsibility for killing his wife due to mental disease or defect. New York uses the ALI standard for criminal responsibility.

Brain scan data had shown a massive cyst in Weinstein's brain. His defense attorney posed the question: Could the brain tumor be responsible for his client's behavior? And if so, did that mean Weinstein was not guilty by reason of insanity? After much counter-punching between defense and prosecution, the court agreed that Mr. Weinstein’s PET scan could be admitted into evidence.

There is no legal record of how Weinstein’s insanity claim fared before a jury because on the eve of trial he agreed to plead guilty to manslaughter. Weinstein was sentenced to seven to 21 years in prison. He was granted a conditional release at age 79 and died two years after his release.

Weinstein’s brain scan revealed Arachnoid cysts that can lead to epilepsy, headache, and other neuropsychiatric impairment. Despite the acceptance of PET in the Weinstein case there continues to be debate concerning the admissibility and the appropriateness of expert witness testimony discussing brain scans in the courtroom.

In a similar instance but with a different outcome in Texas, on December 17, 2014, Eric Williams, a former justice of the peace was sentenced to death for killing a local district attorney, his wife, and a prosecutor. His defense attorney discovered new evidence that an MRI had revealed that part of Mr. William’s brain had atrophied due to prior head trauma thus impairing his ability to regulate his emotions, behavior, and judgment. The judge denied the motion to admit the evidence. The court refused to bring the scan into the courtroom. Texas uses McNaughten.

Similar issues arose in the case of Aaron Hernandez, a former tight end for the New England Patriots, who had been convicted of murdering Odin Lloyd. While on trial for that murder, Hernandez was charged with shooting and killing two other men, although he was later acquitted. Days later he killed himself.

A team of researchers examined Hernandez’s 27-year-old brain. They reported that he suffered the most severe case of chronic traumatic encephalopathy, a progressive degenerative brain disease often seen in people with a history of repetitive brain trauma, they had ever seen in a person his age. While experts are using their customary scientific caution in not connecting Hernandez’s brain pathology to his crime, such severe injuries would have caused poor judgment and lack of impulse control, two hallmarks of the behavior that landed Hernandez in prison for life. Massachusetts uses ALI.

Had it been available neuroscientific data would have evidenced brain abnormality further back in time. Phineas Gage was an American railroad construction foreman in the 1800s who survived an accident in which an iron rod pierced his head, destroying much of his brain's left frontal lobe. The frontal lobe is critical for voluntary movement, expressive language, and for managing higher-level executive functions, such as the capacity to plan, organize, initiate, self-monitor and control one's responses.

Friends reported changes in his personality and behavior for the remainder of his life.‍ This was the first case to suggest the brain's role in deter­min­ing per­son­al­ity, and that damage to specific parts of the brain implies a link between residual brain trauma and personality change.

In 1966 Charles Whitman, stabbed his mother and his wife to death. He then went to the University of Texas Tower in Austin with multiple weapons and began indiscriminately shooting at people. There he fatally shot 16 adults and wounded 31. In writings he left behind, Whitman had complained of headaches and irrational thoughts. He had sought out psychiatric help to no avail. In one of his writings, he requested an autopsy following his death since he expected his rampage would end with his death. Post-mortem he was diagnosed with an astrocytoma brain tumor. The Connally Commission investigating the shooting concluded that the tumor "conceivably could have contributed to his inability to control his emotions and actions."

These cases suggest that our cognitive understanding and decision-making capacities are formed by the capacity of our brains to direct actions.

The expansion of the use of these neurologic tools in the courtroom will allow us to probe more sophisticated questions about the connection between the brain and criminal behavior when evaluating such cases.

Psychiatrists and psychologists have many tools at their disposal that include brain radiography, validated structured interviews, police reports, collateral contacts, neuropsychological, projective, and intelligence testing.

It is the responsibility of American courts to examine all data made available in a case rather than arbitrarily pick and choose what they believe has import in determining guilt or innocence.