Neuroscience in Court: Your Behavior on Trial

My autistic adult daughter stole from the gym we belong to. She went to the drinks cabinet, opened the door, and took a bottle of water on her way to the locker room. Is she guilty of stealing? Yes, physically she stole. However, law is about behavior and the state of mind when committing a crime. In the United States, before someone can be found guilty of a criminal offence, the prosecution must prove that the defendant’s actions when committing the crime were voluntary or purposeful. Further, they must prove that the mental state of the defendant was clear and show that they had intent or knew the act was wrong yet purposely committed the crime. In my daughter’s case, while it was her intent to get a drink, she didn’t understand what stealing was then, nor do I believe she has the concept now. She didn’t want to harm the gym by taking a $1 bottle of water; she was thirsty. She knows we “buy” things in stores, and this was a new gym which she understood we had paid a membership for. She was with me when we signed up and scans her card every time we go. If I were to guess, she probably saw the cabinet as a big refrigerator for the members. What would happen if she was to have faced charges? She is severely autistic, so I would hope a prosecutor would see there was no intent. What about others with mental defects? This is where neuroscience is increasingly making its way into the courtroom, and not just for criminal cases.

Neuroscience and Expert Testimony

According to a recent article in The Atlantic, cases where neuroscience was used in the courts almost doubled between 2005 and 2012 (Miller, 2016), and the outcomes for defendants who relied on neuroscientific evidence were in general more favorable. Clearly, there is a growing need for neurotherapists as expert witnesses. The practice of neuropsychology focuses on the function of the brain as it relates to behavior and cognition, and expert witnesses are thus relied on to convey the limitations and interpretations of neuroscientific findings so that all parties (judges and jurors) can make appropriately informed decisions.

The application of neuroscientific data within the law is complex, however. The timing of neurological tests in relation to the crime can be an important factor. Knowing what section of the brain relates to what type of behavior is also an issue. The occipital lobe, for example, is associated with vision, but the relationship of brain structure and mental processes is not so straightforward. If the majority of neuroscientific evidence is based on statistics and probabilities, proving how it relates to an individual in court is especially challenging. In the United Kingdom, the Royal Statistical Society has published a guide for neuroscience practitioners (see Aitken, Roberts, & Jackson, 2010) covering a range of topics relevant to court proceedings—such as the use of evidence (e.g., What is the question that the evidence purports to be addressing?) and reporting (e.g., Does the expert’s report misleadingly stray into areas of guilt or innocence that should be left to the Court?).

The way that defense lawyers use neuroscience to mitigate or excuse criminal behavior is discussed by Kevin Davis in a recent article in ABA Journal (Davis, 2012) in relation to the events that led to the conviction of Christopher Tiegreen, a disabled man. Tiegreen was 16 years old when he suffered a head injury in a car accident. He had a damaged frontal lobe and sheared brain stem. After coming out of a coma, he became violent. He spent many years in various homes. One day, when he was 23, he escaped from a home and attacked a woman and her infant child. His defense argued he was incompetent to stand trial. The state disagreed, and Tiegreen was required to stand trial. On appeal, the defense argued that the state’s expert only administered the MacArthur Competence Assessment Tool (MacCAT) and did not administer the Fitness Interview Test—Revised (FIT-R), which his own expert had used. The court relied on the expert’s testimony that the MacCAT was the gold standard and concluded that the state did not have to perform the FIT-R. The expert witness also commented that an individual with an IQ of 72 is not automatically incompetent to stand trial. Tiegreen’s IQ was 72. Clearly, in this instance, the expert testimony did not help his case, and it was left up to the court ultimately to decide if Tiegreen was competent. He was eventually sentenced to 30 years in a state-run mental facility. (See for an account of Tiegreen’s appeal.)

“…brains don’t commit crimes—people do.”

Some believe that neuroscience has no place in the courtroom. Stephen J. Morse, Professor of Psychology and Law in Psychiatry, and associate director of the Center for Neuroscience and Society at the University of Pennsylvania, has argued that brains don’t commit crimes—people do. He suggests that neuroscientific research and imaging techniques don’t dictate competence and argues that neuroscience has added virtually nothing relevant to criminal law (Koebler, 2012). I disagree.


Neuroscientific Evidence Mitigates Sentencing

Duke University researcher, Nita Farahany, observed that neuroscience is primarily being used in the courtroom to mitigate punishment, and that defendants with a history of brain injury and trauma claim they have less control over their actions (Koebler, 2012). Hank Greely, director of the Center for Law and the Biosciences at Stanford, further noted that many such cases are appeals where defendants argue they had poor counsel after being convicted—specifically, that they were disadvantaged for not getting a brain scan (Koebler, 2012). But does that argument work?

The case of David Scott Detrich, convicted of murder in the State of Arizona in 2010, is illustrative. Detrich picked up a woman, went back to her place, and then killed her. He was convicted and sentenced to death. He filed multiple appeals that centered around his mental state and how his defense council was ineffective. Why? He argued that they should have offered neuropsychological reports to mitigate sentencing. Detrich had been abused and neglected as a child and suffered as a result of alcohol abuse. The post-conviction court granted funding for a neuropsychological expert, Dr. Robert Briggs. In the report, Dr. Briggs stated that Detrich’s behavior “was not based on any consequence-driven thought process, but rather a leaned [sic] behavior that bypassed right or wrong” (Detrich v. Ryan, 2012, p. 4559). Dr. Briggs further explained that “an interaction between Detrich’s emotional state and mild neuropsychological deficits likely caused a greater overall impairment in function” (p. 4560). Thus, the appellate court held that if Detrich’s trial counsel had sought the assistance of a neuropsychological expert, it would have offered much greater mitigating weight.

I was abused as a child, mentally, emotionally, physically, and sexually. Yes, I have gone to therapy and struggle with anger. At the end of the day, however, I know the difference between right and wrong and make a choice to be of good moral character. Is all mental anguish or disability controllable?

My Brain Made Me Do It

Brain scans were first used to mitigate sentencing in the early ’90s. It was the highly publicized 1991 case of Herbert Weinstein that paved the way for the brain defense. Weinstein confessed to killing his wife, but his attorney pleaded not guilty on his behalf due to mental disease or defect. Weinstein had a cyst on the brain that caused pressure on the temporal lobe, which he argued compromised his self-control. He wanted to present the PET (positron emission tomography) scans as evidence. This was new to the court. To link a defect to behavior based on scans—was it theory or fact? At the evidence motion hearing, the Judge applied the case of Frye v. United States (1923). In that case, the court ruled:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

Once the scans were allowed to be admitted, the prosecutor offered a plea bargain. He argued: “If the jury saw the apparent ‘hole’ in Weinstein’s brain, they might bring a verdict of not guilty by reason of insanity” (cited in Carr, 2017). The murder charge was reduced to manslaughter and the defendant served 7 years in prison. This was the first time that brain imagery was used by the defense. Has it worked in other cases?

Another example is that of a 40-year-old Virginia school teacher who was convicted of child molestation in 2002, but the day before sentencing he was diagnosed with a brain tumor. After the tumor was removed, his impulses diminished and eventually he went home to lead a normal life. Stephen Morse argues that it’s important to distinguish between acting intentionally and acting rationally, and that there is always a reason why people act in a certain way—in this case the man felt an urge that he understood and did not resist (Koebler, 2012). If you don’t act intentionally, however, you’re not responsible. Deciding on this is the challenge for the courts.



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