The Criminal Justice System

Learning Outcomes

  • Understand the three branches of the U.S. criminal justice system

The U.S. Criminal Justice System

A criminal justice system is an organization that exists to enforce a legal code. There are three branches of the U.S. criminal justice system: the police, the courts, and the corrections system.


Police are a civil force in charge of enforcing laws and public order at a federal, state, or community level. No unified national police force exists in the United States, although there are federal law enforcement officers. Federal officers operate under specific government agencies such as the Federal Bureau of Investigation (FBI); the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF); and the Department of Homeland Security (DHS). Federal officers can only deal with matters that are explicitly within the power of the federal government, and their field of expertise is usually narrow. A county police officer may spend time responding to emergency calls, working at the local jail, or patrolling areas as needed, whereas a federal officer would be more likely to investigate suspects in firearms trafficking or provide security for government officials.

State police have the authority to enforce statewide laws, including regulating traffic on highways. Local or county police, on the other hand, have a limited jurisdiction with authority only in the town or county in which they serve.

An armored police officer is shown in a doorway holding and pointing his gun.
Figure 1. Here, Afghan National Police Crisis Response Unit members train in Surobi, Afghanistan. (Photo courtesy of isafmedia/flickr)


Once a crime has been committed and a violator has been identified by the police, the case goes to court. A court is a system that has the authority to make decisions based on law. The U.S. judicial system is divided into federal courts and state courts. As the name implies, federal courts (including the U.S. Supreme Court) deal with federal matters, including trade disputes, military justice, and government lawsuits. Judges who preside over federal courts are selected by the president with the consent of Congress.

State courts vary in their structure but generally include three levels: trial courts, appellate courts, and state supreme courts. In contrast to the large courtroom trials in TV shows, most noncriminal cases are decided by a judge without a jury present. Traffic court and small claims court are both types of trial courts that handle specific civil matters.

Criminal cases are heard by trial courts with general jurisdictions. Usually, a judge and jury are both present. It is the jury’s responsibility to determine guilt and the judge’s responsibility to determine the penalty, though in some states the jury may also decide the penalty. Unless a defendant is found “not guilty,” any member of the prosecution or defense (whichever is the losing side) can appeal the case to a higher court. In some states, the case then goes to a special appellate court; in others it goes to the highest state court, often known as the state supreme court.

Two different courthouse setups are shown here side by side. Image (a) shows a county courthouse for a state trial court. Image (b) shows the courtroom of the Michigan Supreme Court.
Figure 2. This county courthouse in Kansas (left) is a typical setting for a state trial court. Compare this to the courtroom of the Michigan Supreme Court (right). (Photo (a) courtesy of Ammodramus/Wikimedia Commons; Photo (b) courtesy of Steve & Christine/Wikimedia Commons)


The corrections system, more commonly known as the prison system, is charged with supervising individuals who have been arrested, convicted, and sentenced for a criminal offense. At the end of 2010, approximately seven million U.S. men and women were behind bars (BJS 2011d); an estimated 6,613,500 persons were under the supervision of U.S. adult correctional systems in 2016 and the decline is due solely to a declining probation population (the numbers of people in prison, jail, and on probation remain steady). [1].

The U.S. incarceration rate has grown considerably in the last hundred years. In 2008, more than 1 in 100 U.S. adults were in jail or prison, the highest benchmark in our nation’s history. And while the United States accounts for 5 percent of the global population, we have 25 percent of the world’s inmates, the largest number of prisoners in the world (Liptak 2008b).

A map titled "U.S. incarcerates a larger share of its population than any other country" with the subtitle "Incarceration rate per 100,000 people of any age" is shown here. Each country is a shade of brown to represent the rate of incarceration. The US has the highest rate of at 655.5/100,000. The country shown with the second highest rate of 614/100,000 is El Salvador. Countries with the lowest rates (0-99) are found mostly within central Africa.
Figure 3. “America’s incarceration rate is at a two-decade low.” Pew Research Center, Washington, D.C. (May 2, 2018). “U.S. Incarcerates a Larger Share of Its Population than Any Other Country.” Pew Research Center, Washington, D.C. (May 1, 2018).

Prison is different from jail. A jail provides temporary confinement, usually while an individual awaits trial or parole. Prisons are facilities built for individuals serving sentences of more than a year, whereas jails are small and local, prisons are large and run by either the state or the federal government. Increasingly jails operate more like larger prisons, as institutions like Los Angeles County Jail have nearly 20,000 inmates (63 percent of which are non-violent offenders) in seven facilities over 4,000 square miles. Rikers Island in New York City, which sits on a 40-acre complex with ten different facilities (including a juvenile facility), house nearly 14,000 inmates[2].

Parole refers to a temporary release from prison or jail that requires supervision and the consent of officials. Parole is different from probation, which is supervised time used as an alternative to prison. Probation and parole can both follow a period of incarceration in prison, especially if the prison sentence is shortened.

Try It

Dig Deeper

Read this story about Kalief Browder, arrested at age 16 on a robbery charge, held at Rikers Island for more than 1,000 days, including two years in solitary confinement, and then released when his charges were dropped. Read about Kalief’s experiences in jail and what occurred after he was released.

His story has been documented in a six-part Netflix series titled The Kalief Browder Story.

Watch it

Watch the following video from vlogger Hank Green about the messy situation that is mass incarceration in America.


corrections system:
the system tasked with supervising individuals who have been arrested for, convicted of, or sentenced for criminal offenses
a system that has the authority to make decisions based on law
a behavior that violates official law and is punishable through formal sanctions
criminal justice system:
an organization that exists to enforce a legal code
legal codes:
codes that maintain formal social control through laws
a civil force in charge of regulating laws and public order at a federal, state, or community level

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  1. Kaeble, D. & M. Cowhig (2018). Correctional Populations in the United States 2016.
  2. Misachi, J. (updated 2017). The largest jails in the U.S.


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