This study summarizes the current situation, identifies the issues and problems involved in the use of such evidence, outlines proposed solutions, and suggests directions and priorities for future research. The analysis rests on a literature review and on detailed studies of the use of scientific evidence in nine cases: a homicide case, a personal injury case, a civil rights case, an insanity defense case, a questioned-documents case, a Title VII case, an arson case, a ballistics case, and a drug case. Interviews were conducted with over 20 persons involved in various aspects of litigation that uses scientific and technological evidence. Rulings, rules, statutes, informal practices, and factors external to the justice system are identified, with emphasis on how they affect the delivery of state-of-the-art scientific or technological knowledge to the fact-finder. The ways in which this knowledge affects case processing are also discussed. Chapter notes, appendixes presenting State-by-State information and the interview protocols, and a bibliography listing about 850 references are provided.