THE OLD LAW, FOLLOWING THE ILLNESS CONCEPT OF KURT SCHNEIDER, CONSIDERED PSYCHOSES AND SOMATIC PROBLEMS GROUNDS FOR EXCULPATION, WHILE OTHER PSYCHOLOGICAL CONDITIONS WERE NOT RELEVANT TO INCOMPETENCE. THE FOUR GROUNDS FOR INCOMPETENCE IN THE NEW LAW INCLUDE 'PATHOLOGICAL PSYCHOLOGICAL DISTURBANCES,' 'FUNDAMENTAL DISTURBANCES OF CONSCIOUSNESS,' 'MENTAL RETARDATION,' AND 'OTHER SERIOUS PSYCHOLOGICAL ABNORMALITIES.' THESE GROUNDS ARE NOT RANKED ACCORDING TO SERIOUSNESS, AS IT CANNOT BE PROVEN THAT PSYCHOTIC OR SOMATIC ILLNESSES MORE MARKEDLY AFFECT BEHAVIOR THAN EMOTIONAL OUTBREAKS, ABNORMAL PSYCHOLOGICAL CONDITIONS, OR NEUROTIC DISTURBANCES. THE DEGREE OF DEVIANCE FROM THE NORM IS THE DECISIVE FACTOR. THE PSYCHOLOGICAL EXPERT DOES NOT DECIDE ABOUT THE EXISTENCE OF FREE WILL OR ABOUT GUILT, AS THESE ARE PRESUMED BY LAW. THE CONDITIONS OF FUNDAMENTAL DISTURBANCES OF CONSCIOUSNESS AND OTHER SEVERE PSYCHOLOGICAL ABNORMALITIES ARE THE MOST PROBLEMATIC BECAUSE OF THE ALLEGED DANGER OF EXCESSIVE EXPANSION OF EXCULPATION SO THAT EVERY OFFENDER CAN ESCAPE UNPUNISHED. IN ESTABLISHING THE PRESENCE OR ABSENCE OF ABNORMALITIES PSYCHIATRISTS SHOULD AVOID PRESUMING THAT CRIMINAL BEHAVIOR PER SE INDICATES A PSYCHOPATHOLOGICAL STATE OR THAT A MOTIVE CAN PROVIDE GROUNDS FOR EXCULPATION. THE OFFENDERS' MECHANISMS FOR CONTROL OF NEUROSES AS WELL AS THE DEGREE TO WHICH THEY ARE LOCKED INTO HABITUAL RESPONSE PATTERNS SHOULD BE EXAMINED. FOR DISTURBANCES OF CONSCIOUSNESS, PSYCHIATRISTS MUST STUDY THE SITUATION DURING AND AFTER THE CRIME, THE OFFENDER'S PERSONALITY STRUCTURE, THE OFFENDER-VICTIM RELATIONSHIP, AND OTHER POSSIBLE PHYSICAL-TOXICOLOGICAL FACTORS. BECAUSE MENTAL COMPETENCE CANNOT BE MEASURED SCIENTIFICALLY, THE PSYCHIATRIC EXPERT MUST DEPEND ON THE AID OF CONVENTION AND CONSENSUS TO ASSURE JUST LAW. A BIBLIOGRAPHY IS FURNISHED. --IN GERMAN. (KMD)