Comparative criminal justice system is a subfield of study of criminal justice that compares justice system worldwide. Today, comparative research in criminal law is an absolute necessity. In the criminal justice, the only efficacious way to prevent and combat crime is by harmonisation and coordination of all efforts worldwide. A comparative perspective is necessary for overview of powers, laws, punishments and procedure to acquit or convict.

There is a huge impact of comparative criminal justice on public faith, judicature, amendment power of an arrest, structure of criminal judiciary system and reforms.

We often say illegality is an element of crime and government must enact a criminal law specifying the crime and its elements before it inflicts a penalty upon an individual on in requital for criminal behaviour. The plethora of laws differ significantly from state to state. Responsibility for criminal law and criminal justice differs as law is not static. The laws that govern behaviour also changes.