Glossary of Forensic Neuropsychiatry Terms
Plain-English definitions of the neuropsychiatric and legal concepts that recur in brain-injury, capacity, and criminal litigation, written for attorneys handling these cases.
Terms
Neuropsychiatry
Neuropsychiatry is the medical field at the intersection of neurology and psychiatry. It concerns disorders in which brain disease or injury changes cognition, emotion, and behavior. In litigation, a physician trained in it examines the documented brain pathology and the behavioral or psychiatric claim together, as one clinical question.
Relevant to: why retain a forensic neuropsychiatristTestamentary Capacity
Testamentary capacity is the mental ability the law requires of a person making a will: to understand the nature of the act, to know the general extent of the property, and to recognize the natural objects of one's bounty, such as close family. In California it is governed by Probate Code section 6100.5. Capacity is measured at the moment of signing, so a diagnosis of dementia does not by itself defeat a will executed during a lucid period.
Relevant to: testamentary capacity evaluationsUndue Influence
Undue influence is pressure that overpowers a person's free will and substitutes another's intent, so that a will, gift, or transaction reflects the influencer rather than the maker. California's statutory definition, in Welfare and Institutions Code section 15610.70 and adopted for probate matters by Probate Code section 86, weighs the victim's vulnerability, the influencer's apparent authority, the actions or tactics used, and the equity of the result; the common-law presumption of undue influence continues to apply alongside it. Undue influence can invalidate a document even when the maker retained full capacity, because the defect is in the maker's free will.
Relevant to: undue influence assessmentCompetency to Stand Trial
Competency to stand trial is a defendant's present ability to understand the proceedings and to assist counsel in the defense. The governing standard comes from Dusky v. United States: a rational and factual understanding of the charges, plus a sufficient present ability to consult with a lawyer. Competency concerns the defendant's condition now, not at the time of the offense. A finding of incompetence pauses the case for possible restoration; it does not resolve guilt.
Relevant to: competency to stand trial evaluationsCriminal Responsibility (NGRI)
Criminal responsibility asks whether a mental disease or defect, present at the time of the offense, so impaired the defendant that the law excuses culpability, supporting a verdict of not guilty by reason of insanity (NGRI). Standards vary by jurisdiction, but most turn on whether the defendant could appreciate the wrongfulness of the conduct. Unlike competency, criminal responsibility looks backward to the defendant's mental state during the act, which has to be reconstructed from records and clinical evidence.
Relevant to: criminal responsibility evaluationsTraumatic Brain Injury (TBI)
Traumatic brain injury is damage to the brain from an external force, graded mild, moderate, or severe. Severity is classified by acute indices: the Glasgow Coma Scale score, the duration of any loss of consciousness, and the length of post-traumatic amnesia. These acute measures, not later symptom reports, anchor the severity classification. A mild TBI can still be followed by persisting symptoms; the contemporaneous records determine how the injury itself is classified.
Relevant to: TBI litigation expert servicesDiffuse Axonal Injury
Diffuse axonal injury is widespread tearing and stretching of the brain's nerve fibers caused by rapid acceleration and deceleration, as in a high-speed collision. Because the damage is microscopic and scattered, it often does not appear on standard CT and may be missed on routine MRI, showing best on specialized sequences. A normal conventional scan does not by itself exclude this injury; its weight depends on the acute clinical picture.
Relevant to: imaging and TBI causation analysisPost-Traumatic Amnesia
Post-traumatic amnesia is the period after a brain injury during which a person cannot form continuous new memories and is disoriented, ending when day-to-day recall reliably returns. Its duration is one of the primary indices used to grade injury severity, often carrying more weight than loss of consciousness. The window is usually reconstructed from early hospital and witness records, so the contemporaneous notes on confusion and memory gaps largely determine how severity is graded.
Relevant to: severity classification in TBI casesChronic Traumatic Encephalopathy (CTE)
Chronic traumatic encephalopathy is a progressive brain disease associated with repeated head impacts, reported in contact-sport athletes and others with cumulative trauma. CTE is currently a postmortem diagnosis. It is confirmed only by examining brain tissue after death, and no test establishes it in a living person. Claims that a living plaintiff has CTE therefore rest on risk factors and symptom patterns, not on a confirmed diagnosis, and should be framed with that limitation.
Relevant to: repetitive head injury claimsMalingering
Malingering is the intentional production or exaggeration of symptoms motivated by an external incentive, such as money, avoiding work, or evading prosecution. It is a considered judgment supported by convergent evidence, not a label applied from suspicion alone. Malingering differs from genuine illness and from unconscious symptom production. A defensible finding rests on validity measures and on inconsistencies across the records, not on an examinee seeming to overstate complaints.
Relevant to: validity assessment in independent examinationsPerformance Validity Testing
Performance validity testing uses standardized measures, standalone or embedded in a neuropsychological evaluation, to gauge whether a person is putting forth genuine effort. Failing these measures signals that test scores may understate true ability, which undermines reliance on the rest of the battery. Where cognitive impairment is claimed and the question calls for formal testing, validity results often determine how much weight the reported deficits can bear, in either direction.
Relevant to: effort and validity testingFunctional Neurological Disorder (FND)
Functional neurological disorder produces real neurological symptoms, such as seizures, weakness, tremor, or sensory loss, that are not explained by structural brain damage but arise from a disruption in how the nervous system functions. The symptoms are genuine and can be disabling, yet they are distinct from a structural brain injury, so separating functional from structural causes is central to causation. It is diagnosed by positive clinical signs, not merely by the absence of another explanation.
Relevant to: organic versus functional differentiationNeurocognitive Disorder
Neurocognitive disorder is the current diagnostic term for acquired declines in thinking, memory, language, and judgment, ranging from mild impairment to major impairment, the category that includes conditions historically called dementia. The diagnosis alone does not resolve a capacity question: severity, the specific abilities affected, and fluctuation over time all bear on whether a person could make a will, sign a contract, or manage affairs at the relevant moment.
Relevant to: capacity and cognitive declineDiminished Capacity
Diminished capacity is a criminal doctrine under which mental impairment, though not enough to excuse the offense, may prevent a defendant from forming a specific mental state the charge requires, such as premeditation or intent. Where it is recognized, it does not produce an acquittal but can reduce a charge or degree, for example from a higher to a lesser grade of homicide. Availability varies sharply by jurisdiction. California abolished the diminished capacity defense in 1982 (Penal Code sections 25 and 28), though evidence of mental disorder remains admissible on whether the defendant actually formed a required specific intent.
Relevant to: mental state and mitigation analysisFitness for Duty (FFD)
A fitness-for-duty evaluation determines whether a person can safely and effectively perform the essential functions of a specific job, given a medical, cognitive, or psychiatric condition. It is common for physicians, executives, attorneys, and safety-sensitive roles, and often follows illness, injury, or a workplace concern. The question is job-specific and functional. The analysis ties documented impairments to the concrete demands of the role and typically informs return-to-work and accommodation decisions.
Relevant to: fitness-for-duty evaluationsIndependent Medical Examination (IME)
An independent medical examination is an evaluation performed by a physician who is not the examinee's treating provider, retained to give an objective assessment of diagnosis, causation, impairment, or prognosis in a legal or insurance matter. The examiner has no treatment relationship with the examinee, and the opinion is written for the fact-finder. A neuropsychiatric IME pairs record review with examination and validity assessment in a written analysis of brain and behavior.
Relevant to: neuropsychiatric IME servicesEvidence Code 730 Evaluation
An Evidence Code 730 evaluation is one conducted by an expert appointed by a California court under Evidence Code section 730, when the judge determines that expert medical or psychological input is needed on a disputed issue. A section 730 expert is selected by the court and reports to it, unlike an expert retained by one party, and the court defines the questions the expert addresses.
Relevant to: California court-appointed expert workRetrospective Capacity Assessment
A retrospective capacity assessment reconstructs whether a person had the required mental capacity at a past moment, most often after that person has died or declined further, as in a will contest. Because the examiner cannot interview the person at the relevant time, the analysis relies on medical records, financial and legal documents, and witness accounts surrounding the event. How much weight a reconstruction carries depends on how complete and balanced its sources are.
Relevant to: assessing capacity after deathTardive Dyskinesia
Tardive dyskinesia is a movement disorder marked by involuntary, repetitive movements, often of the face, tongue, and limbs, caused by prolonged exposure to certain antipsychotic and related medications. It can be permanent even after the drug is stopped. Its emergence raises questions about the prescribing standard of care: whether the medication was appropriate, whether the patient was monitored for early signs, and whether informed consent addressed this known risk. Timing of onset relative to drug exposure is central to causation.
Relevant to: medication adverse effect litigationExecutive Function
Executive function is the set of higher-order mental abilities that direct behavior: planning, impulse control, judgment, working memory, and shifting between tasks. It depends heavily on the frontal lobes, which are vulnerable in head trauma and in several neuropsychiatric conditions. Executive deficits can impair the ability to weigh consequences or restrain an impulse while leaving basic knowledge intact, which is why they bear on questions of intent, judgment, and behavioral control in criminal and injury cases.
Relevant to: executive dysfunction and behaviorIf one of these concepts is at issue in a matter you are handling, Dr. Lodhi can evaluate how the brain science and the legal standard intersect on your specific facts, for plaintiff or defense. Request a case screening to discuss the case.
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