"A criminal justice system is a set of legal and social institutions for enforcing the criminal law in accordance with a defined set of procedural rules and limitations. In the United States, there are separate federal, state, and military criminal justice systems, and each state has separate systems for adults and juveniles.
Criminal justice systems include several major subsystems, composed of one or more public institutions and their staffs: police and other law enforcement agencies;trial and appellate courts; prosecution and public defender offices; probation and parole agencies; custodial institutions (jails, prisons, reformatories, half-way houses, etc.); and departments of corrections (responsible for some or all probation, parole, and custodial functions). Some jurisdictions also have a sentencing guidelines commission.
Other important public and private actors in the system include: defendants; private defense attorneys; bail bondsmen; other private agencies providing assistance, supervision, or treatment of offenders; and victims and groups or officials representing or assisting them (e.g., crime victim compensation boards). In addition, there are numberous administrative agencies whose work includes criminal law enforcement (e.g., driver and vehicle licensing bureaus; agencies dealing with natural resources and taxation).
Legislators and other elected officials, although generally lacking any direct role in individual cases, have a major impact on the formulation of criminal laws and criminal justice policy. Such policy is also strongly influenced by the news media and by businesses and public-employee labor organizations, which have a major stake in criminal justice issues."
From Criminal Justice System by Richard S. Frase and Robert R. Weidner. Encyclopedia of crime & justice / Joshua Dressler, editor in chief, 2nd Ed., 2002.