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Psychology and The Insanity Defense

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The earliest form of the insanity defense found its footing with 13th, 17th, and 19th century writings from Henry de Bracton, Edward Coke and Matthew Hale, and Henry Roscoe respectively (Maeder, 1985). Bracton, who conducted the first comprehensive study of English law, stated that the law should have provisions extended to both children and “lunatics” when determining sentencings for crimes (Bracton, 1968/ c.1235). Bracton’s writings are emphasized not only because they were some of the first, but also because they were a significant shift from the preexisting theologically-based principles of justice. The earliest stirrings of a possible insanity defense were represented by the gradual shift of focus within criminal trials from simply ascertaining damages to be paid out to the defendant to evaluating the presence of “guilty intent,” or mens rea, within the perpetrator (Maeder, 1985). After a failed attempt to integrate a new standard, or the Durham rule, into the American court system, the rate at which courts deemed defendants to be Not Guilty by Reason of Insanity (NGRI) quadrupled in Washington, D.C.’s District Court. As a result, the American Law Institute (ALI), “a private organization” set on improving legislation, created the Model Penal Code, an attempt to “integrate the criminal justice system according to the most reasonable and generally accepted principles.” (Maeder, 1985). The ALI Model Penal Code continues to undergo revisions and is the prevailing standard upon which most state-level American criminal courts operate today.

As scientific knowledge of human psychology continues to deepen and expand, perspectives of psychological evaluation have grown and adjusted as well. The field of psychology has progressed through multiple editions of The Diagnostic and Statistical Manual of Mental Disorders (DSM), with the DSM-V being the most current edition. These rapid revolutions of psychological knowledge and testing carry powerful implications regarding the testing of sanity, thus begging an important question: To what extent is sanity, or a lack thereof, psychologically evaluated under the standards designated by the ALI Model Penal Code? The legal concept of “insanity” is based upon neither scientifically or psychologically accepted definitions of a lack of personal control due to a mental illness. The presence of a mental illness does not make a criminal inculpable for their offense, but the subject must prove themselves to have lost control of specific mental tasks at the instantaneous time of the crime. The notion that mental incapability can be assessed after-the-fact is neither supported by significant psychological research, nor is it remotely practical to assess immediately. Personality inventories and other forms of testing, some essentially subjective, cannot be considered valid measures of sanity– or the lack thereof. In lieu of solely largely variable testing, reliant on the skill of the assessor and the underlying motivations of the subject, utilizing biopsychological methods to evaluate mental state in conjunction with the already established methods of psychiatric evaluation may prove infinitely more reliable and operational.

II. Analysis A.

Defining Insanity Insanity is not a psychological term, but rather a concept designed for the convenience of sentencing within the justice system. So where does the legal definition of insanity align with diagnoses within clinical psychology? The 1985 revision of the American Law Institute’s (ALI) Model Penal Code waives criminal responsibility if the subject, at the time of the crime and “as a result of mental disease or defect” has a diminished capability “to appreciate the criminality [wrongfulness] of his conduct or to conform his conduct to the requirements of the law.” The legislation provides neither defined guidelines for psychologists or legal professionals in terms of which tests are to be conducted, nor does it clarify exactly what is meant by a “substantial” amount of understanding of moral wrongdoing (ALI Model Penal Code, 1985). Although the ALI Penal Code does not encompass specific mental disorders, disabilities and so forth, many subjects utilizing the insanity defense tend to suffer from either schizophrenia or another paranoid psychological disorder (Slobogin, Melton, & Showalter, 1984). However, the mere presence or diagnosis of a mental disorder does not automatically excuse the subject from criminal culpability. In some cases, the subject will be deemed Guilty but Mentally Ill (GBMI), a verdict that states that the defendant is mentally ill, but still legally responsible for the consequences of their actions. In order to establish this verdict, the state must simultaneously prove the guilt of the subject and find them to be mentally ill, fulfilling traditional legal requirements as well as qualifying the standards within the ALI Model Penal Code. For a defendant to be guilty two components must be present: actus reus and mens rea, or the illegal act and criminal intent (Borum & Fulero, 1999). The subject will also likely enlist a psychological counsel in order to certify the presence of their mental illness. Thus, there are three “levels” of criminal responsibility in terms of the insanity defense and mental illness.

First, there is the possibility that the court rejects the subject’s attempt to plead insanity and they are found to be fully responsible for the crime(s). In this case, they will meet the standards of actus reus and mens rea and fail to fulfill the components of the ALI Model Penal Code. The second outcome and third outcomes, NGRI and GBMI, are almost exactly the same. The only difference between the two is whether their mental illness incapacitated them at the exact “time of such conduct,” meaning at the precise moment of the occurrence of the crime (ALI Model Penal Code, 1985). How does such an imprecise determination decide the difference between a reduced sentence and committal to a psychiatric institution versus traditional sentencing with psychological counsel on an as-needed basis? A solution to the inconsistencies created by the ambiguities of the Penal Code’s legal terminology may be found within an attempt to psychologically quantify and evaluate the sanity of the subject. Although barely synonymous, the closest psychologically-sound substitute for legal insanity may be found within the term “psychopathology.” Psychopathology is defined as a “mental disorder,” presenting in the form of “clinically significant distress, dysfunction, or impairment” in “important areas of functioning” (“Psychopathology,” 2008). Under the Model Penal Code, an individual must be unable to process the criminal nature of their actions or unable to control their actions. In the realm of psychopathology, these requirements may manifest within symptoms such as difficulty with cognitive processing or a lack of inhibitory abilities. Conditions meeting these symptoms may include neurocognitive disorders, schizophrenia, bipolar disorder, and other types of psychosis. The aforementioned disorders may be diagnosed and tested using the slightly more subjective projective tests the Rorschach inkblot test, for example or long-standing, primarily objective, and quantifiable assessments or inventories.

B. Psychological Assessment and Testing Psychological assessment has been an essential component to the field of psychology, beginning with the development of early projective tests and the interview-style interactions popularized by Freud. Criticisms of the lack of empirical evidence to support the two aforementioned forms of assessment led to the quantification of psychological assessment in the form of tests and inventories (Groth-Marnat & Wright, 2016). Modern assessments typically consist of a compiled set of data sources such as interviews, inventories, and more recently, biophysical tests and “aim to collect data to test clinical hypotheses, produce diagnoses, describe the functioning of individuals or groups, and make predictions about behaviors or performance in specific situations.” (Mendes, Nakano, Silva & Sampaio, 2013) Self-reported or scaled assessments consist of typically dichotomous questions that lead to a calculable result at the end. These assessments may include the Minnesota Multiphasic Personality Inventory (MMPI) or the Psychological Screening Inventory. While these assessments do tend to be very clinically-sound and very useful in terms of treating or evaluating individuals not being tried for crime, subjects awaiting trial may have ulterior motives and a not completely unreasonable amount of motivation to exaggerate or malinger symptoms of mental illness while self-evaluating. Even while evaluating non-criminal subjects within an experimental trial, in a study on the associations between over-reporting and scores on the MMPI-2 in a “forensic evaluation context;” individuals tended to over-report “psychopathology,” as well as “somatic/cognitive complaints.” (Rogers & Sewell, 1999). Because the MMPI still maintains its empirical validity within the field of non-criminal psychological evaluation and contains a separate axis for measuring the validity of each individual’s self-reported scores, it is often still used as at least a preliminary screening tool in the legal process. However, relying on a test not specifically meant for the context of forensic evaluation and known to be self-reported may not hold up in the actual courtroom.

In the past, the role of psychologically-trained professionals has often been severely restricted in court because of the difficult nature of measuring and quantifying an individual’s mental capability beyond providing a diagnosis of defined mental disorders. Even more difficult is evaluating whether the individual understood the nature of the crime they were committing precisely at the time the incident took place. While thorough, the aforementioned screening procedures are not often conducted with the sole purpose of preventing criminal activity in mind. Typically, and rightfully so, psychiatric evaluation is centered on improving the life of the client and bringing their symptoms down to a manageable level. In addition to not being designed specifically for use in forensic settings, tests requiring self-reporting or self-evaluation involve the possibility of subjects malingering, or feigning symptoms associated with a mental illness in order to garner a less severe sentence. The Rogers Criminal Responsibility Assessment Scales (R-CRAS) are less of an intervention-based device and are specifically created for use in a forensic setting (Rogers & Sewell, 1999). The R-CRAS integrate both an interview and a quantified assessment into a model that addresses five principle areas: “Patient’s Reliability (e.g., reliability of patient’s self-report under voluntary control), Organicity (e.g., presence of brain damage or disease), Psychopathology (e.g., anxiety), Cognitive Control (e.g., planning and preparation), and Behavioral Control (e.g., responsible social behavior).” (Roesch, Viljoen, Hui & Hui, 2003). A reexamination of the Rogers Criminal Responsibility Scales (R-CRAS), conducted by its creator Dr. Richard Rogers and Dr. Kenneth W. Sewell, attempts to discern patterns that “differentiate loss of cognitive control from volitional control.” Rogers and Sewell analyzed the data from 413 cases involving insanity pleas in with the R-CRAS were utilized. These cases applied the version of the R-CRAS that had been adapted to include “five additional variables” contained in questions 26 through 30 that addresses the widely used McNaughton standards.

The added questions addressed “judgement, behavioral disturbances, reality testing, capacity for self-care, and awareness of wrongfulness.” (Rogers & Sewell, 1999). The R-CRAS have been consistently modified and monitored over time, along with updated by the actual author and his colleagues. Rogers’ report also contains a statistical analysis of the entire test, along with each subsection or axis, documenting the variable or symptom that each item on the questionnaire attempts to measure. Although the R-CRAS have received some criticism for quantifying answers and creating linkages between scores and criminal tendency, their reliability and validity have been maintained across multiple reviews and studies over time. The R-CRAS are tailored to both the ALI Model Penal Code and the older McNaughton standards for determining criminal culpability when presented with the insanity defense.

C. Biophysical Symptomology and Detection In addition to evaluating mental disorders and their corresponding symptoms through psychological evaluation, newer and more empirical forms of detection may prove to be extremely useful implements. In the instance of some disorders, such as schizophrenia, the disorder may be detected through various forms of neuroimaging because of genetic heritability, documented “structural variations,” and neurochemical abnormalities (van Os & Kapur, 2009). Non-invasive forms of brain imaging, specifically magnetic resonance imaging (MRI), have even been used to detect neurological abnormalities within certain regions of the brain (Bennett, 2009). Using imaging techniques, specific areas of the brain have been linked to actually being able to voluntarily control one’s own behavior. “Inhibitory control deficits,” or the lack of the ability to regulate one’s behavior is significantly pronounced even within individuals with disorders that do not entail psychosis or delusion and they may possess deficits in other mental functions such as memory, learning, or planning (Bora, Harrison, Yücel, & Pantelis, 2012). Under the rule of the ALI Model Penal Code; however, the simple identification of limitations in regard to mental function does not indicate a complete inability to understand the gravity of legal consequence. Nonetheless, the detection of a neurological abnormality does begin to lessen the possibility that the individual’s symptoms or lack of self-control are malingered. To combat the gray area between substantial and insubstantial capacity to understand legal parameters or limit behavior, one may couple with neurological tests the previously mentioned psychological evaluations, the R-CRAS, in order to receive a more complete psychiatric profile of each individual and to truly use their best judgement in order to provide the court with an opinion of the individual’s sanity. Empirically identifying the inability to delay impulsive behaviors and control behavior would satisfy not only the conditions of the ALI Model Penal Code but would also encompass the requirements of the other forms of the insanity defense utilized in the United States.

III. Conclusion

The difficult relationship between the legal system and field-specific experts is no more apparent than in the field of forensic psychology. Spanning the gap between the two studies while maintaining proper ethical considerations for those concerned; however, must remain a constant priority. While simply revising the ALI’s Model Penal Codethus editing the foundational text for most U.S. state courts to include stated mental disorders may be the most convenient option, it hardly takes into consideration the stigma already surrounding individuals with mental illnesses or disorders. In order to combat further bias, one must take into consideration the glaring dilemma created before an individual is even evaluated by a psychiatric professional in order to determine their sanity in criminal terms. Additionally, the fact that the ALI Penal Code has been effective for such a lengthy amount of time and functioned well within the system does not do much to confirm it as a reliable way to test for cognitive function within the accused, but in the event that it cannot be changed, psychology may need to adapt to better treat individuals deemed by the court to be NGRI and thus given time in a psychiatric institution.

Continued statistical analysis and clinical review of the methods of psychological assessment for both criminal and non-criminal standards are essential, for both the well-being of the patients and society as a whole. A combination of cognitive and humanistic therapy methods, along with the aid of psychopharmacology, may better the treatment of individuals declared to be Not Guilty by Reason of Insanity or even Guilty but Mentally Ill. Moving forward, the field of psychology has also begun to take into consideration the measurement and analysis of neurological and biophysical portions of the subject’s brain matter and analyzing any criminal tendencies or loss of control or function that may take place as a consequence of damage or underdevelopment. In order to limit any sort of evaluation bias and to prevent malingering to the highest extent possible, taking into consideration both a mandatory psychiatric evaluation of the individual using one standardized system, perhaps R-CRAS or another specifically-formulated assessment, and a complete neurological/genetic profile will provide the most rational and objective appraisal of true cognitive ability and function. Focusing on building an established understanding between professional psychological experts and the legal community. Understanding that the subject is not only a party within a court case, but also an individual that may be in need of professional help and/or psychological treatment. The ability to prevent and deal with criminal activity come not only from having a well-run justice system, but also from understanding the mental roots of criminal activity and the inner psychology behind certain acts.

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Psychology and the Insanity Defense. (2019, August 27). GradesFixer. Retrieved January 27, 2022, from
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