Reasons for the continued existence of discretion include overcriminalization in the criminal code, the severity of criminal sanctions in the United States, law enforcement considerations, and the economic impossibility of full enforcement of existing laws. A study of actual discretionary practices by prosecutors' officers suggests that four policies underlie the manner in which prosecutorial discretion is exercised in the decision to charge. The first policy -- legal sufficiency -- is a porous filtering process at the intake stage of the criminal justice system. The second policy -- system efficiency -- has the goal of retaining organization control, efficient management, and accountability. The third policy focuses on defendant rehabilitation and relies on noncriminal justice system resources and community support to assist in moving eligible defendants out of the criminal justice system. The fourth policy -- trial sufficiency -- focuses on making a charge in the initial system encounter that the prosecutor expects to stick with throughout the trial. Although abuse of prosecutorial discretion can jeopardize important societal values and make a mockery of justice, discretion nonetheless fulfills valuable functions otherwise unobtainable in the administration of justice. Internal guidelines would provide meaningful and effective parameters within which prosecutors could operate, and the involvement of more than one prosecutor in charging decisions would facilitate uniformity.