How Does the Criminal Justice System Work?

How does the criminal justice system work in the United States?

Overview of Criminal Justice System

By the time they reach 23 years old, nearly one-third of Americans have been arrested for some type of crime. If you represent one of the 33% of Americans that have spent time behind bars, you understand the criminal justice system can be confusing at best and extremely intimidating at worst.The American criminal system consists of three primary components:
  • Crime
  • Litigation
  • Incarceration
In short, a criminal case starts with one or more law enforcement agencies investigating crime. If there is enough evidence to file charges, the case goes on the docket of a criminal court. The last step is to determine guilt or innocence and if the defendant is found guilty, some type of punishment is handed down by a judge or a jury.


A crime as defined in the American criminal justice system can be an act or a failure to act, depending on the legal language of a state or federal statute. At the heart of criminal law is the United States Constitution, which protects American citizens against law enforcement actions such as illegal search and seizures. Although many crimes are offenses against individuals or organizations, legislatures that enact laws and government agencies that enforce state and federal statutes consider crimes to be against society.Here are some of the law enforcement agencies that can be involved in charging someone with a crime:
  • City Police Department
  • County Sheriff Department
  • State Police Agency
  • Federal Law Enforcement Agencies
Federal law enforcement agencies include the Federal Bureau of Investigation (FBI) and the Bureau of Alcohol, Tobacco, Firearms, and Explosives.


Lawyers that represent local, state, or federal government law enforcement agencies are referred to as prosecutors of criminal cases. Prosecutors are responsible for sifting through evidence to determine whether there is enough proof to move forward with the filing of criminal charges. After filing charges against a defendant accused of a crime, prosecutors then plot the legal strategy for prosecuting the case in a criminal court.There are three types of prosecutors:
  • Federal
  • State
  • Local
Federal prosecutors represent the interest of the United States Department of Justice. They enforce laws passed at the federal level, with the help of Assistant United States Attorneys. States prosecutors work for each of the 50 states and they enforce criminal laws that are applicable to the state they represent. Attorneys responsible for enforcing state criminal statutes are licensed in the state they represent. Local prosecutors enforce laws passed by cities, which typically are ordinances that cover a limited geographical area.


The outcome of a criminal trial can render several different decisions. A defendant charged with a crime can be found not guilty or placed on probation, which means the defendant is set free, but he or she must follow numerous strict guidelines to remain outside the boundaries of a prison. Defendants that are sentenced to jail spend time at a correction facility operated by a state government or a federal government agency. Each criminal sentence differs, with the number of years mandated by a court for the defendant to spend incarcerated being the most significant sentence differing factor. Correction officers monitor prisoners, as well as make sure each prisoner follows the sentencing guidelines established by a criminal court.

Burden of Proof

The burden of proof is always placed on the prosecution of a criminal case. Attorneys representing the state must submit compelling evidence, such as eyewitness testimony and revealing physical evidence, to prove a defendant’s guilt beyond a. reasonable doubt. The reasonable doubt litmus test of guilt means that under the American criminal justice system, the prosecution must prove its case “beyond a reasonable doubt.” The reasonable doubt concept is also referred to as beyond a shadow of a doubt.

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