The insanity defense: Related issues

Area of Science:

• Forensic Psychology
• Neuroscience
• Criminal Law

Background:

• Criminal liability has historically centered on the concept of free will and the capacity to discern right from wrong.
• Alternative theories, positing behavior as an interaction of biological and environmental factors, have struggled for acceptance within the criminal justice system.
• The insanity defense, a long-standing legal concept, has evolved through various tests, with historical formulations like McNaughton's rules emphasizing intellectual understanding of right and wrong.

Purpose of the Study:

• To evaluate the adequacy of current legal standards for criminal liability in light of modern neuroscience.
• To explore the limitations of rationality-focused legal tests, particularly the neglect of impulse control and volitional capacity.
• To propose improvements for juror decision-making in criminal responsibility assessments.

Main Methods:

• Review of historical legal tests for criminal responsibility, including McNaughton's rules.
• Analysis of current understanding of neurological evidence related to compulsion and impulse control.
• Examination of the concept of "evidentiary relevance" and expert testimony quality control.

Main Results:

• Traditional legal tests for criminal responsibility, focusing on rationality, appear outdated given neurological evidence of compulsion and lack of impulse control.
• Current legal frameworks may neglect crucial aspects of volitional capacity, impacting the accuracy of assessments.
• The concept of "Relevance ratio" is suggested for "evidentiary relevance," alongside quality control for expert testimonies.

Conclusions:

• Neuroscience advancements challenge fundamental legal assumptions about voluntary conduct underlying criminal defenses.
• Legal standards for criminal liability may require significant revision to incorporate findings on impulse control and biological/environmental influences.
• Implementing separate "Control determination" and "Rationality determination" for jurors could enhance the accuracy of legal judgments regarding criminal responsibility.