Forensic Psychiatric Diagnosis UNMASKED
Greenberg, Stuart A., Shuman, Daniel W., Meyer, Robert G., Judicature
The forensic use of psychiatric diagnoses in expert testimony by psychiatrists and psychologists is common. But what role should diagnoses play in psychiatric and psychological testimony? When do diagnoses assist and when do they confuse in the forensic setting? This article critiques the forensic use of psychiatric diagnostic categories found in the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) as well as other diagnostic categorization systems. This is not a critique of the DSM itself nor of the non-forensic uses of psychiatric diagnoses. It is a critique of the forensic application of a categorical approach to describing a litigant's psychiatric status.
What is the role of the diagnosis of mental disorders in the legal system? Whether someone is properly labeled as having a particular diagnosis is a clinical issue; whether that classification should serve as a legal determinant for competence, compensation, or commitment is a legal issue. It is for the law to decide if a particular diagnosis should be an essential element in one legal context and not in another. Whether Posttraumatic Stress Disorder or Antisocial Personality Disorder qualify as mental illnesses for the purpose of the Americans witli Disabilities Act, civil commitment, or criminal responsibility are separate questions that may well call for different responses.1 Psychiatric diagnoses do not play the same role in all legal contexts; the same psychiatric diagnosis may be of consequence in one area of the law but not another.
In some instances, such as the insanity defense, civil commitment, and the Americans with Disabilities Act, the law makes diagnosis an essential element of a claim or defense. Most codifications of the insanity defense require the presence of a severe mental disease or defect and exclude character or personality disorders. When, as in the case of the insanity defense, diagnosis is an essential legal element of the defense, and when a proper foundation for that diagnosis exists, diagnosis becomes an appropriate topic for expert testimony.
In other instances, such as personal injury litigation, child custody litigation, and testamentary or contractual competence determinations, the law does not make diagnosis an essential element of a claim or defense. Instead, legal criteria for these actions are functional and concern themselves with impairment or capacity without regard to diagnosis. In these actions, the presence of diagnosis does not, in and of itself, create or defeat legal claims or defenses. In these cases, where testimony as to diagnosis is used circumstantially, the appropriateness of expert testimony about the presence or absence of a diagnosis is not as clear.
The appropriate purpose of the presentation of psychological and psychiatric testimony is to clarify; however, ironically, that testimony is often confused by the use of diagnoses. The focus on diagnoses may also provide additional incentives for litigants to reframe the presentation of their injuries and incapacities. This is particularly ironic since these diagnostic categories exist to help clinicians and researchers communicate with clarity and precision.
The creation of a diagnostic classification scheme of almost any design is an inherently daunting task if for no other reason than, while the essential task is to group like persons, nature abhors clear boundaries.2 Valid and reliable diagnostic grouping requires both specificity and sensitivity. In order to not falsely include persons within a diagnostic category, the criterion set must include symptoms that are most useful in discriminating one disorder from similar disorders (and thus achieve high specificity) while the set must also include the symptoms that are most characteristic of the disorder (and therefore achieve high sensitivity). Emphasis on high sensitivity results in groups that are composed of members that have salient characteristics in common but, in failing to exclude persons who are coincidentally similar, results in multiple categories to which many persons may correctly be designated. …