Insanity on Trial: The Legal Construction of the Insanity Plea
The insanity plea is defined as a defense that can be pleaded in a criminal trial, in which the defendant can admit the action but deny legal responsibility for it on account of mental illness. The defense has been controversial due to landmark cases, such as the M’Naughten case, Durham v. United States, and countless more where it is believed the plea had been abused, or contained the potential for abuse. One of the major complications is born from the impossible nature of insanity as a concept; within neuropsychology, the definition hinges upon the legal benchmarks established, and no formal definition is recognised in The Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR). [1] Kahler v. Kansas states that legal insanity is best described as a legal concept, not a psychological one. [2] This case examined whether the constitution required a specific definition of insanity, with Kahler arguing that Kansas’ classification of the insanity rule ignored ‘cognitive incapacity’ that was recognized in psychiatry. The court had ruled that they could define insanity in ways they best see fit, such as the moral-incapacity test, rather than conform to psychiatry’s definitions. Courts treat insanity as legal issue, but the intersection with neuropsychology has been underappreciated, and with developments in research, courts may need to reconsider their level of involvement in the intersection. Many cases that utilize this defense rely on the idea that the defendant had been in psychosis (characterised by delusions, hallucinations and formal thought disorders), and due to this cannot claim culpability for the actions they have admitted to. The insanity plea remains a complicated concept in criminal law as it relies on a tension between neuroscience and law: while courts rely on neuropsychological evidence to assess a defendant's mental capability, legal insanity is ultimately shaped by legal standards rather than clinical definitions; this tension ultimately leads to implications for new legal cases as new research emerges connecting the two doctrines.
Landmark cases shape our understanding of the plea within the court system, and understanding the steps taken in the rulings of these cases aids in our modern grasp of the plea. The first case of the insanity plea being used in the United States was the case of People v. William Freeman heard and decided by the New York Supreme Court. [3] In 1846, Sarah Van Nest had been attacked and killed outside her home by a man with a knife, Her husband, John, had attempted to rescue her but was instead stabbed and murdered alongside her by the assailant. The assailant was then accused of entering the home and murdering Sarah’s mother and child, totalling four murders. The assailant had then been confronted with a guest in the house, where they fought before the man escaped the scene.
William Freeman had been sentenced prior to five years in prison to hard labour for stealing a horse. During his time in prison, he frequently engaged in heated disputes with security guards and received countless beatings. The frequent dispute led to him receiving a severe brain injury that caused mental confusion and deafness. Freeman was accused of committing the four murders, as he was found forty miles from the scene. William H. Seward, a lawyer who defended Freeman’s case, believed that Freeman had a mental illness and therefore should not claim culpability for his actions. His mental confusion was labelled as insanity, with a witness testifying the difference in Freeman’s mental facilities prior and post-injury, as well as medical experts who testified to Freeman’s symptoms of insanity. Despite Seward’s efforts, the jury found Freeman competent for trial, and the case continued.
In a medical setting, neurological scanning is frequently used for psychiatric patients. This abundance of information allows us to identify potential differences in the brains of individuals, including many that may use the plea. Recent research has examined whether neuroimaging can attempt to improve the identification of criteria to declare insanity and therefore increase objectivity in legal defense. Current cases have currently remained speculative, “Our claim is that the use of neuroscience and behavioral genetics do not change the rationale underlying the determination of criminal liability, which must be based on a causal link between the mental disorder and the crime. Rather, their use is crucial in providing objective data on the biological bases of a defendant's mental disorder.” [4] New research has found that individuals who have committed murder have been found to have reduced gray matter. [5] Gray matter refers to regions of the brain composed of neuronal cell bodies and glial cells, it is what we use to think, make decisions, and process information, especially in the frontal lobes.
A study at the University of Chicago had looked at brain scans of hundreds of incarcerated individuals, all convicted for homicide or homicide attempt, aggravated battery/assault, armed robbery and many other violent crimes as well as baseline individuals who had not committed violent crimes or minimally violent crimes. [6] It was shown that individuals who had committed homicide or attempted homicide had reduced grey matter, especially when compared to individuals who had committed other crimes, or none at all. The reductions in the grey matter were most commonly seen in frontal regions associated with behavioural control, emotional processing and social cognitions. The research has yet to establish a causal link, remaining correlational at this stage. The reduced matter may be labelled as the driving force that causes individuals to commit the crimes due to the reduced ability of decision making and emotional processing. There may also be other factors yet to be studied that mediates these findings. Kiehl and Decety’s research is ongoing, in hopes of establishing a more concrete causal link between homicidal behaviour and predictive neurological factors, which in turn will have great implications for the legal system and hopefully the insanity plea. It is unclear if neurological research will progress to fully explain and remove culpability from those who commit the crimes, but the progression may aid in establishing more concrete understanding to aid in accurate sentencing.
McElrath v. Georgia serves as a more recent example of where the insanity defense is used in the modern legal system and how the system requires specific distinctions in order to proceed with such a plea. [7] Damian McElrath was diagnosed with bipolar disorder and ADHD at a young age shortly after being adopted by his single mother Diane. Damian reportedly exhibited limited responsiveness to psychiatric treatment and was notably inconsistent with taking prescriptions. Through his teen years he exhibited behavioural problems in school and with law enforcement as well as general low performance in school. At 18, he committed the murder of his mother due to a delusional belief that she had been actively poisoning him. There was a notable decrease in Damian’s mental stability in the years approaching 2012, with an increase in delusions that led him to be committed to a facility to be diagnosed with schizophrenia but shortly discharged. McElrath stabbed Diane only one week after his release and explained he did so due to his belief of her poisoning him.
The state of Georgia charged McElroy with malice murder, felony murder and aggravated assault. In trial, McElrath admitted to the murder but asserted the insanity defense, a defense recognised under Georgia law. The insanity defense is recognised as following “A person shall not be found guilty of a crime when, at the time of the act, omission, or negligence constituting the crime, the person, because of mental disease, injury, or congenital deficiency, acted as he did because of a delusional compulsion as to such act which overmastered his will to resist committing the crime.” [8] Even if the defendant does not meet an insanity defense, the jury may find them “guilty but mentally ill,” which requires temporary mental health treatment, rather than a longer term commitment associated with the insanity plea.
These specific distinctions serve as an example of the complicated nature of the plea. In recent times through social media, the plea is associated with a ‘get out of jail free card’, seeing the psychiatric holds as a lesser sentence. This may not reflect the reality, with a multitude of issues related to the underfunding of mental health facilities, social stigma as well as it is found that those in a psychiatric hold are often held considerably longer than others convicted of the same crime. [9]
McElrath v. Georgia concluded with inconsistent verdicts from the jury, finding McElrath not guilty by reason of insanity on the malice murder count, and guilty but mentally ill on the felony murder count. This led to a new trial, where the Supreme Court ruled 9-0 in favour of McElrath. [10] The court held that a verdict of not guilty by reason of insanity counts as an acquittal, and the Double Jeopardy Clause of the Fifth Amendment would prevent the retrial of that charge, and the verdict still stands, preventing a retrial on McElrath's malice murder charge. The case demonstrates how the modern insanity defense proceeds procedurally, rather than conceptually.
As neuroscientific research progresses, the insanity plea faces new implications for future cases, raising questions on how legal proceedings concerning insanity may have to adapt alongside emerging evidence. Neuroscience’s contributions currently progress in helping understand how to identify brains that are predisposed to harmful tendencies as evidenced through reduced frontal lobe activation. Yet there is little concrete integration of the neuropsychological concept of insanity within the legal system, the process emphasizes the procedural element built upon years of prior rulings. Kahler v. Kansas is clear in establishing how the law may not adjust to extend for related concepts.
Though, with a potential for emerging research, could neuroimaging evidence provide stronger support in the definition of legal insanity? Courts may need to adapt to consider biological markers when evaluating cases more heavily as the research is refined and causal relationships begin to develop. It would allow more quantitative evidence to support juries in determining a verdict, allowing for less conversation on incorrect or inconsistent verdicts.
Looking ahead, the legal system at large must work alongside mental health professionals to establish clearer guidelines for the interpretation of neuropsychological research. This would ensure that research would inform but not dictate legal determinations. Neuroscience may provide and refine understanding of mental illness and how it impacts behaviour, the insanity plea is likely to remain fundamentally legally based.
One other consideration for the insanity plea, is that as social media evolves, there is increase in conversation surrounding mental illness, and the stigma that accompanies it, all of which may impact juries. With conversations about psychiatric disorders and mental health becoming increasingly visible online, jurors may hold preconceived notions regarding mental health, whether positive or negative. Greater awareness could aid in understanding and empathy when considering individuals with psychosis or other cognitive impairments, or could result in oversimplifications and stereotyping, which could reinforce ideas of violent personalities being intertwined with mental illness, both outcomes have the possibility of impacting a jury's perception in cases. The rise of research and understanding being accessible has great potential, but consequences accompany it, all of which has real impacts on the legal system, especially with a plea as controversial as the insanity plea.
The insanity plea remains a complex intersection of many doctrines, shaped by legal precedent as well as evolving scientific research, and there does not seem to be a concrete answer on whether it will adapt. From historical cases such as People v. Freeman, to more modern rulings such as McElrath v. Georgie, courts have adapted the insanity plea to prioritise legal definitions over clinical or neurobiological interpretations of mental illness to determine culpability. Emerging research in neuroimaging offers some potential to provide causal insights into brain function and impulse control, which may inform courts in its assessment of culpability. Emphasis must be placed on the potential to inform, but not replace judicial assessments. Alongside the neurological research as well as established legal precedent, factors such as social perceptions of mental illness must remain a factor to be actively considered. While neuroscience and social perception may refine how the insanity plea can be evaluated, it is at its core, a legal construct that balances scientific evidence alongside it. The ongoing challenge for courts as research and social media evolves will be to integrate these developments in order to adapt, while also ensuring verdicts remain consistent and grounded primarily in the law despite the complexity of evaluating the human mind.
Sources
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Arlington, VA: American Psychiatric Publishing, 2013.1.
Kahler v. Kansas 589 U.S. (2020)
People v. Freeman, 242 N.Y. 401 (1926).
Rigoni, D., S. Pellegrini, V. Mariotti, A. Cozza, A. Mechelli, S. D. Ferrara, P. Pietrini, and G. Sartori. 2010. “How Neuroscience and Behavioral Genetics Improve Psychiatric Assessment: Report on a Violent Murder Case.” Frontiers in Behavioral Neuroscience 4: 160.
A. Sajous-Turner et al., “Aberrant Brain Gray Matter in Murderers,” Brain Imaging and Behavior 14, no. 5 (2019): 2050–2061
Rygoodwin. 2019. “Scientists Studied the Brains of More Than 800 Prisoners. Here’s What They Found.” University of Chicago News, July 23, 2019.
McElrath v. Georgia, 601 U.S. (2024).
Ga. Code Ann. §§ 16-3-2, 16-3-3, 17-7-131(c)(1) (2019).
Pogrebin, Mark, Robert Regoli, and Ken Perry. 1986. “Not Guilty by Reason of Insanity: A Research Note.” International Journal of Law and Psychiatry 8 (2): 237–241.
McElrath v. Georgia, 601 U.S. (2024).