Lay participants are persons who have neither education in legal issues nor training in legal decision making; they are selected to decide legal cases either with fellow lay participants or with the professional judges. Some countries assign the responsibility of conducting trials in serious criminal cases and deciding legal issues to professional judges, and lay participants have the responsibility of deciding the facts (the jury system). Other countries assign all of these functions to a tribunal composed of both professional judges and lay participants; however, even in countries with very extensive systems of lay participation, there is a tendency to treat less serious cases differently in order to reduce the expenses associated with trials. This can be achieved either by assigning only the least serious cases to be tried by lay persons, by reducing the size of the decision making group, or by replacing the decision making group with only one individual, a professional judge. This paper begins with a general consideration of lay participation from an idealistic perspective and discusses reasons for the introduction of lay participation into the legal decision making process. The paper further describes lay judges in mixed tribunals from a more realistic, pragmatic view that is based on a systematic overview of the research results on topics such as the lay judges' contribution to the verdicts and general opinions on mixed tribunals. 32 references