Proposition: a personality disorder may nullify responsibility for a criminal act.

Area of Science:

• Forensic Psychology
• Psychiatry
• Neuroscience

Background:

• Current legal frameworks often exclude personality disorders from insanity defenses.
• Debates persist regarding categorical versus dimensional diagnostic approaches.
• Neurocognitive and behavioral genetics research informs understanding of mental disorders.

Purpose of the Study:

• To argue against per se rules barring personality disorder diagnoses in legal insanity defenses.
• To advocate for a focus on case-specific functional deficits arising from mental disorders.
• To address implications for expert testimony and legal fact-finding.

Main Methods:

• Literature review integrating diagnostic controversies, neurocognitive science, and behavioral genetics.
• Conceptual analysis of legal insanity defense standards.
• Examination of differential diagnosis and comorbidity challenges.

Main Results:

• Per se exclusion of personality disorders in insanity defenses is scientifically and conceptually flawed.
• Focusing on diagnosis over functional deficits leads to misleading expert battles.
• Current practices risk improper judicial deference to mental health experts.

Conclusions:

• Legal insanity defenses should consider functional deficits caused by personality disorders.
• A shift towards assessing specific impacts of mental disorders is recommended.
• Policy proposals for managing defendants found not guilty by reason of insanity are considered.