The criminal justice system has three main parts:
- law enforcement (police)
- adjudication (courts)
- corrections ( prison, jails, parole, and probabion)
Criminal justice is primarily concerned with the enforcement of criminal law. Criminal law is concerned with actions which are dangerous or harmful to society as a whole in which prosecution is pursued not by an individual, but by the state. Criminal law defines specifically what constitutes a crime and what punishments should be prescribed for committing any particular crime. No criminal law can be valid unless it includes both of these elements.
The misconception that the police are primarily concerned with enforcing criminal law came about in the 1930s with the creation of the Federal Bureau of Investigation, a "law enforcement agency." However, this activity of policing is only one of many policing activities. The main activities of police involve order maintenance and provision of services.
As an academic discipline, criminal justice is a separate study from criminology; it combines the study of practical and technical policing skills with the study of social deviance as a whole, thus including basic courses in the areas of psychology, sociology, and criminology.