THIS INTERVIEW WITH A PROFESSOR FROM THE UNIVERSITY OF COLORADO WHO IS A RECOGNIZED EXPERT IN FORENSIC CHEMISTRY CONSISTS OF A SERIES OF RECOLLECTIONS OF CASES IN WHICH HE HAS PARTICIPATED. HIGHERLY TECHNICAL ASPECTS OF DRUG ANALYSIS, DRUG-RELATED DEFENSE TESTIMONY, AND CRIMINAL INVESTIGATION ARE PRESENTED IN AN INFORMAL MANNER. THE STORIES TRACE THE ACCEPTANCE OF MASS SPECTROMETRY AND OTHER SOPHISTICATED CHEMICAL TESTS IN THE COURTROOM. TECHNIQUES WHICH PROVED SUCCESSFUL FOR BOTH THE PROSECUTION AND THE DEFENSE ARE RECALLED. IT IS EMPHASIZED THAT TO BE BELIEVED, THE EXPERT WITNESS MUST PRESENT THE TESTIMONY IN A SIMPLE MANNER WITHOUT INSULTING THE INTELLIGENCE OF THE JURY. THE STORIES ALSO ILLUSTRATE THE VARIOUS EFFORTS DEALERS IN ILLICIT DRUGS USE TO CIRCUMVENT RESTRICTIVE LEGAL LANGUAGE, SUCH AS SYNTHESIZING VARIATIONS OF COMMON DRUGS. DRUG DETECTION AND ANALYSIS IS REVIEWED INFORMALLY. THE USE OF EXPERT WITNESSES IS URGED, BUT ONLY IF THE WITNESS IS WELL PREPARED AND FAMILIAR WITH COURTROOM PROCEDURE. (GLR)