Mental impairment is a widespread phenomenon amongst criminal defendants. But the legal requirements for an insanity defense are rarely met in U.S. or German criminal cases. Thus, legislators and judges are asked to reconcile the rationale of imposing sentences that are proportionate to the severity of an offense and the individual culpability with the demand to ensure public safety. As a functional legal comparison, the book discusses not only explicit statutory rules on diminished capacity but the various dogmatic approaches to accommodate the impact of mental impairment on criminal responsibility short of insanity in the U.S. and Germany. To provide a useful tool for legal professionals, mental disorders are systematically analyzed with regard to their symptoms, causes, forensic relevance and diagnostic methods. Based on the conclusions of her research, the author presents specific suggestions to improve legal concepts for dealing with mentally impaired offenders in Germany.