Guide to the U.S. Criminal Justice System

Written by: Nalea J. Ko | Edited by: Cassie Muniz | Last Updated: April 2024

What Is the Criminal Justice System? | Law Enforcement | Courts | Corrections | Tribal Law | How the System Works | Careers | FAQ

• The criminal justice system includes the courts, corrections, and law enforcement.
• Full-time law enforcement accounts for more than 700,000 U.S. workers.
• The federal court includes 94 district courts, 12 circuit courts, and the U.S. Supreme Court.
• U.S. Department of Justice and the U.S. Department of Homeland Security comprise the federal law enforcement.
• The first prison system in the country opened in 1891.

What Is the Criminal Justice System?

The criminal justice system in the United States consists of law enforcement, the court system, and corrections. These three subsystems encompass private and government agencies at the state, federal, and local levels, all of which work together to maintain public safety.

Each subsystem handles a different responsibility. Law enforcement does as their name implies: they enforce the law by making arrests. At the court level, defendants undergo the trial process that includes the opening statements, presenting of evidence, closing arguments, and sentencing. Convicted persons undergo rehabilitation as part of the correction process.

This comprehensive guide explores the complex network of subsystems within America’s criminal justice system.

Law Enforcement in the United States

At every level, the law enforcement branch of the United States criminal justice system attempts to serve the public by promoting safety and order. Law enforcement officers investigate suspected criminal activities and refer suspected criminals to courts.

The three main levels of law enforcement include federal, state, and local (e.g., county and municipal) policing. Each level tends to works independently within its own jurisdiction.

Each law enforcement level maintains internal hierarchies of individual departments and ranked officers who supervise and report to one another. To learn more about the structure, varying roles, and goals of each of these law enforcement levels, continue reading.

Federal Law Enforcement

The federal branch of law enforcement includes thousands of full-time officers working within dozens of federal agencies. The two main departments that employ law enforcement officers are the U.S. Department of Justice (DOJ) and the U.S. Department of Homeland Security (DHS). Notable agencies associated with each department include:

Local and state law enforcement handle the majority of crimes in the U.S., but the federal government steps in where states and municipalities lack jurisdiction, such as when perpetrators commit crimes on federal property.

More specifically, the 10th Amendment to the U.S. Constitution reserves all rights and powers for the states that are not expressly delegated to the federal government. States reserve the right to establish and enforce laws to protect public health, safety, and welfare.

Thus, federal police power typically extends only to situations involving:

• Civil rights
• Patents
• Immigration
• Offenses affecting interstate commerce
• Crimes committed across state lines

State Law Enforcement

Most states operate law enforcement initiatives through agencies and departments extending from a few central government entities. For example, a state’s department of public safety generally sees to the services and duties of state police and highway patrol.

Each state has an office of the attorney general, which handles the criminal and civil detective work of a state’s bureau of investigation and works as the state-level equivalent of the FBI.

A variety of other departments within state governments can operate their own divisions of law enforcement, especially for security purposes. The most common of these include:

• State capitol’s capitol police force
• Universities employing campus police
• State hospital security staff

When considering the role of state police, people commonly think of highway patrolmen, but the purpose and goals of state law enforcement extend beyond pulling over speeding cars.

State police conduct enforcement activities and investigations that fall outside the jurisdiction of a county sheriff’s office. Duties beyond highway patrol and enforcement of traffic laws may include:

• Protecting government officials
• Arresting suspects
• Providing emergency assistance
• Protecting crime scenes
• Interrogating or interviewing people

Local and Municipal Law Enforcement

Among the various sections of the criminal justice system, local law enforcement is the branch that a majority of people are most familiar with. Unlike federal and state law enforcement branches, local law enforcement operates within specific counties, cities, and communities.

The structure of local law enforcement can vary greatly depending on the jurisdiction size. A small town — like Ellendale, Delaware or Little River, Kansas — may employ a single officer or town marshal, whereas major cities like New York City have a large police department spread throughout multiple neighborhood precincts.

Counties often establish a sheriff’s department and county police force with a wider jurisdiction and/or greater focus on jail and court services, rather than patrolling a specific town or neighborhood.

Depending on the size of a local police department, the hierarchy can include up to a dozen different positions. A police commissioner — also called the chief of police — stands at the top of the chain of command. This position is followed by an assistant chief, deputy chief/commissioner, inspectors, colonels, majors, captains, lieutenants, sergeants, detectives, and officers or deputies.

Court and Legal Systems in the United States

The United States criminal justice system consists of courts at the federal and state levels. Federal and state courts are independent of one another and differ in several key areas defined by their jurisdiction and the types of cases they hear.

State courts receive a broad jurisdiction, hearing cases regarding:

• Family disputes
• Broken contracts
• Traffic violations
• Criminal activities (assaults or robberies)

In contrast, federal courts commonly hear cases in which the U.S. is a legal party:

• Federal law or Constitutional violations
• Bankruptcy
• Copyright and patent law
• Maritime law

U.S. courts work closely with law enforcement and corrections in scenarios such as deciding whether or not to hear a case, sharing intelligence, asking law enforcement officers to testify during a trial, engaging in presentencing investigations, and determining alternative sentencing options.

State Courts

The vast majority of criminal and civil legal cases in the U.S. are handled by the massive state court system. Each state divides its courts into a structure with three main tiers: trial courts, appellate courts, and state Supreme Courts.

Trial courts include municipal courts (limited jurisdiction). Typical cases include:

• Traffic court
• Misdemeanor crimes
• Preliminary felony hearings

County courts (larger jurisdiction). Cases may relate to:

• Family law
• Probate law
• City ordinance violations

State trial courts (largest jurisdiction). Cases may relate to:

• Probate law
• Family law
• Property disputes
• Major felonies

When a losing party disagrees with a trial court’s decision, they can file an appeal. This prompts the trial court to send the case record to a state appeals court for consideration. To make a final ruling decision, the appellate court does not conduct a trial, instead relying on case documents, trial transcripts, exhibits, and attorneys’ written arguments.

An appellate court can either affirm the original decision, reverse the original decision, or send the case back to a trial court for further action.

A legal party unhappy with the ruling of their appeal can take the case a step further by requesting a final appeal with the state’s Supreme Court. At this level, appeals remain discretionary. The court decides whether or not to hear a case; if it declines, the lower court’s decision is considered final.

A state Supreme Court functions similarly to lower appeals courts. It reviews case documents, files, written briefs, and oral arguments rather than holding a full trial.

Upon reviewing a case, the state Supreme Court either affirms a decision, reverses it, or sends a case back to trial. Legal parties who do not receive their desired appeal result can strive for a final appeal with the U.S. Supreme Court.

Federal Courts

Three main levels make up the U.S. federal court system: 94 district courts, 12 circuit courts, and the U.S. Supreme Court. District courts conduct civil and criminal trials within the federal system, with one or two assigned to each U.S. state or territory. Trial cases commonly heard in district courts include those dealing with federal laws and/or those involving parties from two different states.

Like the state court system, legal parties who disagree with the decision of their district court trial can file for an appeal. A circuit court acts as the first stop in the federal appeals process. Some appealed cases receive decisions based on a review of court records and written briefs alone; however, many are also selected for oral arguments, in which attorneys can briefly present spoken arguments before a panel of judges.

The circuit court decision remains final unless the case is sent back for trial or legal parties seek an appeal with the U.S. Supreme Court by filing a petition for a “writ of certiorari” — simply put, a request for judicial review.

Each year, the U.S. Supreme Court receives thousands of requests for case review, but selects only a small fraction to hear. Cases most commonly heard by the Supreme Court include:

• Cases with an unusually significant legal principle
• Cases where at least two federal courts differ in the interpretation of a law
• Cases interpreting the Constitution

Once the U.S. Supreme Court delivers a decision, it can be overturned only by a rarely granted request for a rehearing, a future Supreme Court ruling, or an amendment to the Constitution itself.

Corrections in the United States

While law enforcement and the courts work to identify and intercept people involved in criminal activity, the corrections system serves a variety of simultaneous functions:

• Keeping criminal populations separate
• Enacting punishments for wrongdoing
• Promoting rehabilitation for the incarcerated

The U.S. corrections system is the largest system of its type in the world. Though home to less than 5% of the world’s population, the U.S. holds more than 20% of the world’s prisoners — the highest global per capita rate of incarceration among founding NATO countries, according to 2021 incarceration data.

The U.S. corrections system contains multiple state and federal corrections systems that act independently, although they follow similar procedures and protocols. Prisons can be publicly or privately operated, and state and federal corrections systems most commonly interact when transferring inmates. Corrections systems utilize incarceration, community service, parole, and probation to punish and/or rehabilitate criminals.

Incarceration entails the confinement of a person in a prison, and daily prison life severely restricts that person’s freedoms. In contrast, those sentenced to community service or those on parole or probation live beyond a prison cell.

If assigned to community service by a court, an individual typically completes a number of unpaid work hours for a nonprofit. Parole and probation both involve supervision and specific rules/guidelines regarding travel limitations, curfews, and required drug tests. Parole typically occurs when an individual gains early release from prison, while probation occurs before an individual enters prison.

The U.S. holds a high rate of recidivism, meaning the likelihood that a convicted criminal will return to prison is relatively high. This most commonly occurs because people violate the terms of their parole, and perhaps because the American rehabilitation system has inherent flaws.

There hasn’t been a large-scale recidivism survey conducted yet this decade, butfor 2019, BackgroundChecks.org places the U.S. recidivism rate of 70% within five years of initial incarceration.

Tribal Law in the United States

Federally recognized Native American tribes possess a form of sovereignty that preserves the inherent rights of each tribe to form their own governments, make and enforce civil and criminal laws, collect taxes, and establish and regulate tribal citizenship.

Some of the first federal recognitions of tribal sovereignty and law began in the early 19th century with a series of Supreme Court decisions, including the 1832 case of Worcester v. Georgia.

Though this case did not prevent the relocation of the Cherokee Nation from its ancestral homeland, it served as a foundation for the principle of tribal sovereignty, with the majority opinion calling tribal nations “distinct, independent political communities retaining their original natural rights.”

While federal Native American law concerns relationships between tribal, state, and federal government, tribal law governs a tribe’s members and territories. Tribal governments and tribal justice systems function in much the same way as state systems.

Tribal law is enforced by tribal law enforcement, and tribal courts that possess civil jurisdiction over tribal members and nonmembers who reside or do business within federal reservations. In 1978, the criminal jurisdiction of tribal courts became limited to violations of tribal law by tribal members only (Oliphant v. Suquamish Indian Tribe). Along with operating their own law enforcement and courts, Native American reservations house more than 90 corrections facilities.

Today, tribal governments, laws, and areas of jurisdiction often function in partnership with their local and state counterparts, working together to promote public safety and economic development. In some cases, however, the division between tribal and state jurisdiction can cause difficult legal complications.

How Does the Criminal Justice System Work?

A standard series of steps — including investigation, charging, initial hearing, discovery, plea bargaining, trial, sentencing, and appeal — helps streamline the process from law enforcement to the courts to corrections. The sections below explain those steps.

1) Entry Into the Criminal Justice System

The criminal justice process begins when someone commits a crime. Law enforcement officers on patrol can witness a crime directly, or be dispatched to respond to a witness’s call about a potential crime.

When officers arrive on the scene, the second step involves filing a crime report, which includes logging information about the time, location, and details of the incident by speaking with witnesses and/or victims.

This process must be completed as accurately and precisely as possible, as it builds a foundation that can impact the subsequent investigation and arrest of a suspect. It may also determine who gets called to testify in a trial and the sentencing process.

After obtaining a crime report, law enforcement can begin the process of investigation, arrest, and/or citation. If the suspect remains on site, officers can provide a citation with a date to appear in court or they can arrest the suspect.

Otherwise, officers must pursue an investigation and attempt to identify a suspect and collect enough direct or circumstantial evidence to warrant an arrest. If officers complete an investigation, discover a suspect, and collect appropriate evidence, they can make an arrest or provide a citation, depending on the nature of the crime and other factors.

2) Prosecution and Pretrial

The decision to formally charge a person with a crime rests with a court prosecutor, who forms this determination by examining all assembled evidence and a suspect’s criminal history. If a prosecutor does not find a suspect guilty beyond a reasonable doubt, that suspect is released. Alternatively, if a prosecutor decides to file formal charges, they determine the severity of the alleged crime (e.g., a murder charge versus a manslaughter charge).

If a suspect faces charges, an initial hearing will typically take place within 72 hours. A first court appearance involves arraignment, whereby the court informs a defendant about their legal rights and the charges they face.

The defendant responds to arraignment by entering a plea of guilty, not guilty, or no contest (allowable in some jurisdictions). A guilty or no contest plea means the defendant receives a sentence without going through the trial process. A not guilty plea means a case proceeds toward trial.

Upon a plea of not guilty, the defendant and court make defense attorney arrangements, if this has not already been done, and the judge determines if the defendant will be held or released. Depending on the severity of the charges and other factors, defendants may be given the option to post bail.

3) Trial Process

Rather than going to trial, a majority of cases in the criminal justice system are resolved by a plea agreement. Arranged cooperatively between the prosecution and defense, a plea agreement means the defendant agrees to plead guilty to one or more charges in exchange for a recommendation of a reduced sentence, a lesser degree charge, or having one or more charges being dropped entirely.

If parties do not reach a plea agreement, the case proceeds to trial.

Defendants reserve the right to select a jury trial (decided by a group of civilians) or a bench trial (decided by a single judge). A majority of defendants select bench trials. Reasons for this may include a speedier process — no need for jury selection, minimized opening/closing statements, lower mistrial risk — and/or concerns that a jury may judge the case based on emotion rather than on evidence/the law.

In either trial method, the prosecution and defense present their arguments and witnesses testify and face cross examination. Trials close with the judge or jury deciding on a verdict. Not guilty verdicts lead to the defendant’s release, while guilty verdicts lead to a sentence. If a jury cannot deliver a verdict due to disagreement or other reasons, such as misconduct or illness, a mistrial is called and a new trial can be arranged.

4) Corrections

To determine the appropriate sentence for a guilty defendant, a judge can examine sentencing guidelines provided by the United States Sentencing Commission.

For situations involving less serious crimes and shorter sentence lengths, judges may decide to sentence convicted persons to probation or parole rather than incarceration.

Probation or parole come with supervision and other restrictions. For example, individuals may face limitations on where they can live and travel, requirements to hold steady employment or attend school, and/or requirements to attend therapy or rehab. Violating probation or parole terms can land an offender in jail or prison.

Though controversial, a sentence of capital punishment remains legal in 27 states. However, this sentence can only be handed down by the unanimous decision of a jury, and it is only applicable in cases of capital offense (e.g., murder and/or assassination, treason, and espionage).

Careers in Criminal Justice

Criminal justice careers encompass many law enforcement, legal, and correctional roles, including jobs that only require a high school diploma and on-the-job training and those that require years of college study.

A majority of criminal justice professionals obtain at least a bachelor’s degree. However, many schools offer criminal justice degrees at multiple levels, including master’s and doctoral programs for students interested in higher-level management, academia, or research.

Criminal justice professionals tend to be detail oriented, inquisitive, and highly organized and possess a natural affinity for leadership and problem solving. The list below details several criminal justice-related careers.

Frequently Asked Questions About the Criminal Justice System

What is the criminal justice system in simple terms?

The criminal justice system adheres to policies and practices that exist to uphold justice and keep people safe. The criminal justice system operates to prevent crime and punish law offenders under the governing jurisdiction. The criminal justice system is the complicated network of legal subsystems at the federal, local, and state level in the United States.

How has the criminal justice system changed over time?

The criminal justice system and the policies that influence mass incarceration shifted during the War on Drugs that began nearly 50 years ago. In 2023, politicians enacted policies to reduce mass incarceration, including reforming sentencing for youth defendants, increasing parole eligibility, and changing policies to reduce punitive practices put in place during the War on Drugs. Some states are working on restoring voting rights to former felons.

What is the definition of “justice” in the criminal justice system?

Justice as it relates to the criminal justice systems means ensuring that all people receive fairness in the legal process. The United States Constitution protects every citizen’s right to justice. According to the Sixth Amendment, all citizens have the right to a lawyer and a fair and speedy trial in front of an impartial jury.

What is the purpose of the U.S criminal justice system?

The U.S. criminal justice system exists to enforce laws but also to protect all citizens and society. The saying goes, “crimes against an individual are crimes against the state.” The criminal justice system outlines penalties for criminal behavior with the aim of deterring crime. When the courts find criminals guilty, judges sentence them to prisons or jails for rehabilitation.

Is the FBI part of the criminal justice system?

Yes. The Federal Bureau of Investigation (FBI) operates under the U.S. Department of Justice. The FBI often works with other law enforcement agencies to share intel, especially in cases of national security threats. The Director of National Intelligence oversees the operations of the FBI, which reports intelligence to local U.S. attorneys.