AbstractThere is a biological basis for diminished criminal responsibility in offenders with fetal alcohol spectrum disorders (FASD) just as there is in those with intellectual disability. Functional limitations affecting cognition in both neurodevelopmental conditions stem directly from structural brain damage at a gross and molecular level, which usually impairs executive functioning among other cognitive skills. Executive functioning, which includes reasoning and impulse control, is the only neural system in the brain that involves consciousthought. With respect to the law, impaired reasoning or rationality is an aspect of mens rea (“guilty mind”). When rationality is impaired by prenatal alcohol exposure, acts driven by strong emotion and urges can occur, which has obvious implications regarding criminal responsibility. TheAtkinsdecision by the U.S. Supreme Court reflects the rationale that organically based brain dysfunction in executive skills reduces criminal culpability. We argue that people with FASD who have similar brain dysfunction likewise have reduced criminal responsibility.