In New York State, Mental Hygiene Law defines mental illness as "an affliction with a mental disease or mental condition which is manifested by a disorder or disturbance in behavior, feeling, thinking, or judgment to such an extent that the person afflicted requires care, treatment and rehabilitation." (1) It has long been acknowledged that individuals suffering from active symptoms of mental illness might not be fully responsible for their actions. This concept manifests in criminal law, as with the insanity defense, and also in civil arenas. Examples include the competence to make certain personal choices, such as making wills, choosing among treatment options, and being civilly committed.
The concept of diminished personal responsibility as a result of mental illness has historically been articulated in standards regarding the insanity defense, ranging from the M'Naughten Test to the American Law Institute Test. (2) Regardless of the exact standard, the underlying reasoning is that mental illness, by impairing a person's ability to think rationally or control behavior, arguably impacts the degree to which he is truly able to make choices independently and, by extension, is responsible for his behavior.
The role of mental illness in individual behavior and personal responsibility, however, is far from straightforward. There are instances where mental illness and its relationship to violent or criminal behavior are clear; take for example an individual who commits an act in response to delusional beliefs. Among mental health professionals, it is well accepted that psychotic illnesses and major mood disorders, diagnoses traditionally included within the category of serious mental illnesses ("SMI"), have the potential to lead to behaviors for which an individual may not be fully responsible. These illnesses have biological factors that are documented throughout the scientific literature, and, for the most part, have established effective, if imperfect, treatment regimens comprised of medications and other therapies. (3) It is also known that symptoms of mental illness vary in severity and may wax and wane over the natural course of the illness. Therefore, the mere presence of a diagnosis does not necessarily equate to lack of responsibility for behavior. Mental illness may account in part or in full for behavior, or may only be coincidental to that behavior. While it is important that individuals who are unable to think rationally or control behavior as a result of mental illness are not criminally sanctioned, it is also necessary to recognize that many individuals who have mental illness can in fact function competently and rationally when not symptomatic. There are also those who function well even while experiencing mental health symptoms. No diagnosis is in and of itself synonymous with functional incapacitation, symptoms fluctuate over the course of illness, and the degree of impact varies greatly from one person to the next. In that sense, failure to recognize that individuals with mental illness can be responsible for their own decisions contributes to the stigma of mental illness.
Treatment advancements beginning in the 1970s, including improvements in psychopharmacology, increasingly supported the notion that symptoms of SMI are often transitory and controllable. Legal requirements, such as the least restrictive level of care standard in commitment criteria as articulated in the landmark case Lake v. Cameron, (4) required changes in commitment practices with advances in symptom management. (5) Subsequent court decisions established protections for civil commitment hearings, as exemplified by Lessard v. Schmidt, (6) which established procedural requirements, and by Addington v. Texas, (7) which established the standard of proof necessary for involuntary civil commitment.
While court decisions have increasingly protected seriously mentally ill individuals from involuntary commitment or retention in a psychiatric facility without significant due process, a series of legislative actions, bolstered by court decisions, simultaneously increased the involvement of the mental health system in the treatment and control of criminally involved individuals, particularly those diagnosed with serious personality disorders. …