This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.

Contribute Thoughts | Search Serendip for Other Papers | Serendip Home Page

Biology 202
2003 Second Web Paper
On Serendip

The Insanity Defense- Should it be judged legally or medically?

Priya Raghavan

Former U.S president Ronald Reagan was shot by a man named John Hinckley in the year 1981. The president along with many of his entourage survived the shooting despite the heavy infliction of internal and external injuries. The Hinckley case is a classic example of the 'not guilty by reason of insanity' case (NGRI). The criminal justice system under which all men and women are tried holds a concept called mens rea, a Latin phrase that means "state of mind". According to this concept, Hinckley committed his crime oblivious of the wrongfulness of his action. A mentally challenged person, including one with mental retardation, who cannot distinguish between right and wrong is protected and exempted by the court of law from being unfairly punished for his/her crime. (1)
What is "insanity" and why is this subject of much controversy? Although I do not have a clear definition of insanity, most socially recognized authorities such as psychiatrists, medical doctors, and lawyers agree that it is a brain disease. However, in assuming it is a brain disease, should we link insanity with other brain diseases like strokes and Parkinsonism? Unlike the latter two, whose causes can be medically accounted for through a behavioral deficit such as paralysis, and weakness, how can one explain the behavior of crimes done by people like Hinckley? (2)
Much of my skepticism over the insanity defense is how this act of crime has been shifted from a medical condition to coming under legal governance. The word "insane" is now a legal term. A nuerological illness described by doctors and psychiatrists to a jury may explain a person's reason and behavior. It however seldom excuses it. The most widely known rule in the insanity defense refers to the M'Naghten rule which arose in 1983 during the trial of Daniel M'Naghten who pleaded that he was not responsible for his murders because he suffered from delusions at the time of the crime.
The rule states, " A defendant may be excused from criminal responsibility if at the time of the commission of the act, the party accused was laboring under such a defect of reason, from a disease of mind, as not to know the nature and the quality of the act he was doing..." (3)

The problem with this defense is that insanity here is either examined from a legal angle or a psychoanalytical one which involves talking to people and having them take tests. There is however, no scientific proof confirming the causal relationship between mental illness and criminal behavior based on a deeper neurological working of the brain sciences. The psychiatrist finds himself/herself in a double bind where with no clear medical definition of mental illness, he/she must answer questions of legal insanity- beliefs of human rationality, and free will instead of basing it on more concrete scientific facts. Let me use a case study to elaborate my argument that law in this country continues to regard insanity as a moral and legal matter rather than ones based on scientific analysis.
The insanity defense of Andrea Yates: The country was absolutely appalled when it heard that Yates, a mother of five children, had killed each of her children resulting in a horrific family slaughter. There were extremely polarized feelings about this case- sympathy (concluding that there must have clearly been some uncontrollable behavior) vs. retribution, punishment vs. treatment. What causes a human being to behave and act in such a manner? The criminal justice system and modern science approach the question with interestingly different perspectives. The M'Naghten rule allows little room for negotiation of the crime details. Essentially, the defendant is declared either sane or insane; the defect of reason from a brain disease makes them either right or wrong. The dichotomy left no shades of gray until the 20th century. Advances in the field of neuroscience indicated that certain mental diseases were caused in part by factors outside the control of the individual inflicted with the disease and the fact that medication could be used to successfully alter one's behavior was a scientific breakthrough. (4)
The legal system, feeling quite insufficient on its part, developed modern laws such as the "Irresistible Impulse" which included diseases like kleptomania, and pyromania, and the Durham test in 1954 which stated that the defendant is insane only if his/her criminal charges was a product of a mental disease or defect." The legal system that created the latter law readily removed it from practice after noticing that mental health experts had too big a role in determining what caused the defendant to commit the crime, but seldom answered as to what produced the action. Lawyers felt that left to the doctors and psychiatrists, the very notion of criminal charges and responsibility would be softened because all such behavior would then be categorized a mental illness.
It was the John Hinckley case that re-popularized the tough rule of the M'Naghten creating an ambiguous relationship between law, psychiatry, and neuroscience. Insanity, at the end of the day is a legal determination. The fact that the legal system had the authority to form and terminate the various laws of defense shows that it is a very malleable system of practice.
"Contradictions inevitably emerge where the laws of man are confused with the laws of nature: The former can be broken; the latter cannot. These contradictions are what make the "insanity defense" in a trial like that of John Hinckley Jr. appear to be an affront to justice and common sense." - Donald E. Watson (5)

Nonetheless, in today's insanity cases, mental health experts, doctors, and scientists have important roles to play. They can inform the jury of the nature of the defendant's mental illness, the likeliness that the crime might be repeated, and whether the defendant may bring harm upon himself/herself. However, like any court case, there will always be divided opinions amongst the mental experts regarding the outcome of the case depending on whether they testify for or against the defendant.
The key to balance "insanity" from a legal standpoint to a more medical one is for a breakthrough in neuroscience where well organized causal connections between mental illness and criminal act is established and made mandatory. There has been progress with medical experts introducing new concepts including the Battered Women Syndrome which recognize abusive conduct against women resulting in acts of self-defense.
One might wonder if criminals use the insanity defense to escape punishment?
Perhaps this skepticism on relying on legal methods in determining an "insane" person's fate calculates the fact that there are extremely few insanity cases and even fewer successful ones in reality. For instance, in the 1970s, a study in Wyoming revealed that the insanity defense was used in only .47% of all criminal cases (Melton, 1997, p.187) (6)
Moreover, in the same study it was observed that only one person, of those that used the defense, was acquitted. In the legal realm, insanity and sanity stand in a reversible state. When the defendant no longer tests positive in legal tests, an insane person miraculously becomes sane. Unfortunately, the same law does not account or recognize the physical, emotional or psychological states that may or may not be reversible.


1)All About the Insanity Defense, Mark Godo

2) Does Insanity "Cause" crime? : Thomas Szasz, M.D., The Myth of Mental Illness (1960)

3)M'Naghten Rule

4)The Yates case: Commentary for United Press International; Susan Crump is a former prosecutor for Houston

5) Donald E. Watson, MD taught and did research in nueropsychology, teaches at UC Irvine Medical School.

6) Statistics

| Course Home Page | Course Forum | Brain and Behavior | Serendip Home |

Send us your comments at Serendip

© by Serendip 1994- - Last Modified: Wednesday, 02-May-2018 10:53:04 CDT