COURTS ARE BECOMING INCREASINGLY CONCERNED WITH THE EFFECTS OF DRUGS ON BEHAVIOR AND SHARE A NATURAL RELATIONSHIP WITH PSYCHOPHARMACOLOGY IN THAT BOTH FIELDS ARE CONCERNED WITH THE RULES FOR MAN'S DRUG USING BEHAVIOR. ON THE SURFACE THE TASK OF THE DRUG ABUSE EXPERT WITNESS IS TO SHARE WITH THE COURT HIS EXPERT KNOWLEDGE ON DRUGS AND THEIR RELATION TO SOCIAL CONDUCT AND BEHAVIOR. HOWEVER, THIS KNOWLEDGE MUST BE EXPRESSED IN LEGAL TERMS AND MUST ADDRESS LEGAL QUESTIONS; THIS RESTRICTION MAY COMPROMISE SCIENTIFIC MEANINGS. THE MOST COMMON LEGAL ISSUE CONFRONTING THE EXPERT IS THAT OF CRIMINAL RESPONSIBILITY. HERE, THE RULES OF THE COURTS SUCH AS THE M'NAUGHTEN AND DURHAM RULES HAVE TRANSFORMED INTO LEGAL REALITY THE PRECONCEIVED NOTIONS THAT THERE ARE TWO MODES OF EXISTENCE, SANITY AND INSANITY. ACCORDINGLY, DRUG-INDUCED BEHAVIOR MUST FALL INTO ONE OF THE TWO CATEGORIES. WHILE PROSECUTORS FREQUENTLY DECLINE TO PROSECUTE FOR CRIMES COMMITTED BY MENTAL PATIENTS, DRUG ABUSERS HAVE NO SUCH PROTECTED STATUS DESPITE THE FACT THAT BOTH MENTAL PATIENTS AND DRUG INTOXICATED INDIVIDUALS MAY ACT RATIONALLY AT TIMES. THE DRUG ABUSER IS VIEWED BY THE CRIMINAL JUSTICE SYSTEM AS A PERSON LACKING ADEQUATE INTERNAL CONTROLS OVER HIS DRUG USE. THIS FACT HAS LED TO RITUAL PERSECUTION OF DRUGS, ADDICTS, AND PUSHERS. THEREFORE, AN APPROPRIATE FUNCTION OF THE FORENSIC PSYCHOPHARMACOLOGIST IS TO EDUCATE THE COURTS AND TO INFORM THEM THAT DRUGS ARE NOT THE CAUSES OR SYMPTOMS OF MENTAL ILLNESS. DRUGS ARE SIMPLY SUBSTANCES WITH CERTAIN CHEMICAL PROPERTIES AND BEHAVIORAL POSSIBILITIES AND PROBABILITIES. REFERENCES ARE PROVIDED. (AUTHOR ABSTRACT MODIFIED--LWM)