Guide to the U.S. Criminal Justice System


What is the Criminal Justice System?

The modern American justice system developed through years of change and increasing structuralization. From its original form as colonial crime codes based on religious doctrine, the United States criminal justice system evolved into the complex entity we recognize today. The need for increased supervision caused informal, communal watchmen to evolve into paid, trained professionals in uniform who must toe the line between authority figures and community members. Rapid urbanization and growing populations forced the creation of larger federal and state court systems that ultimately replaced small colonial courts, and biblical crime codes progressed into extensive books of local, state, and federal laws.

Today, the criminal justice system comprises thousands of individual systems with varying jurisdiction: city, county, state, federal or tribal government, and military installation.

Today, the criminal justice system comprises thousands of individual systems with varying jurisdiction: city, county, state, federal or tribal government, and military installation. Three major components of the criminal justice system — law enforcement, courts (including prosecutors, defense attorneys, judges, and juries), and corrections — allow each division to function independently or in collaboration. Modern goals of the criminal justice system include preventing crime, protecting the public, supporting victims of crimes, holding perpetrators responsible for crimes committed, and helping offenders return to society as law-abiding citizens.

The sections below go into greater detail about the structure and makeup of the United States criminal justice system and how the criminal justice process works, from crime to corrections. Popular criminal justice careers are also discussed.

Frequently Asked Questions

What is the justice system?

The criminal justice system consists of law enforcement agencies, court systems, and corrections systems, which span federal, state, and local levels of the U.S. government.

How does the justice system work?

The criminal justice system operates within the three major components described above. Law enforcement officials begin work when a crime is committed by conducting an investigation. This is followed by the court process and then the corrections system, if needed.

Structure and Components

To better examine the structure of American criminal justice, a more detailed look at each of the three primary components becomes necessary. The main components of the criminal justice system include law enforcement, courts, and corrections. Additional levels with varying jurisdiction, including local, state, and federal levels, exist within each of these components, but each division generally adheres to the same overarching goals. Law enforcement works to prevent crime, courts strive to enact justice when a crime is committed, and corrections focuses on retribution and rehabilitation. This criminal justice system flowchart details the common sequence of events.

Beyond the three main components, the state and federal levels of the United States criminal justice system are structured into a hierarchy of various departments and agencies. State systems commonly consist of an attorney general’s office, departments of public safety, state police and highway patrol, and college campus and capitol police. The federal system includes the Department of Justice, the Department of Homeland Security, and a number of federal agencies and law enforcement groups that report to these departments (e.g., the FBI, U.S. Marshals Service, and U.S. Customs and Border Protection).

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.

Federal officers, for example, can handle larger-scope domestic or international threats, while state and local police primarily work on smaller-scale investigations and crime prevention in counties, cities, and municipalities. 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 the sections below.

Federal Law Enforcement

The federal branch of law enforcement includes two main departments, dozens of individual agencies, and thousands of full-time officers. The U.S. Department of Justice (DOJ) maintains the greatest level of responsibility for upholding federal law enforcement; this is executed through many agencies, including the FBI; Drug Enforcement Administration; Federal Bureau of Alcohol, Tobacco, and Firearms; U.S. Marshals Service; and Federal Bureau of Prisons.

Other important federal law enforcement agencies, including the TSA, Secret Service, U.S. Customs and Border Protection, and Immigration and Customs Enforcement, report to the U.S. Department of Homeland Security (DHS). The Coast Guard also reports to the DHS, except in times of war when its assignments transfer to the U.S. Department of Defense (DOD).

Local and state law enforcement handle the majority of crimes in the U.S. The federal government steps in where states and local 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 and prohibited for the states. States reserve the right to establish and enforce laws to protect public health, safety, and welfare. Thus, federal police power typically only extends to situations involving civil rights, patents, immigration, offenses affecting interstate commerce, and crimes committed across state lines.

Many U.S. citizens never fully realize the dramatic impact that federal law enforcement officers make on their daily lives. Additionally, some of our most common interactions with federal officers — such as at TSA checkpoints in airports — hold a societal reputation of being an annoyance or inconvenience. Nonetheless, federal law enforcement officers play an important role in maintaining public safety and order.

State Law Enforcement

Most states operate law enforcement initiatives through agencies and departments that extend from a few central government entities. A state’s department of public safety generally sees to the services and duties of state police and highway patrol. Each state also utilizes an office of the attorney general, which handles the criminal and civil detective work of a state’s bureau of investigations 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 sites employing capitol police, university campuses employing campus police, and state hospitals employing 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 and work to uphold public safety and order. Duties beyond highway patrol and enforcement of traffic laws may include protecting government officials, arresting suspects, providing emergency assistance, protecting crime scenes, and interrogating or interviewing individuals.

Local and Municipal Law Enforcement

Among the various sections of the criminal justice system, local law enforcement represents the branch that a majority of people are most familiar with. Unlike federal and state law enforcement branches, which handle large jurisdiction areas, local law enforcement exists to operate 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 only employ a single officer or town marshal, whereas major cities like New York City boast 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 employed 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. Though each level follows similar procedures within the criminal justice process, federal and state courts remain independent of one another and differ in several key areas; these are mainly defined by their jurisdiction and the types of cases they hear.

State courts receive a broad jurisdiction that allows them to hear cases regarding family disputes; broken contracts; traffic violations; and criminal activities, such as assaults or robberies. In contrast, federal courts commonly hear cases in which the U.S. is a legal party; cases dealing with federal law or Constitutional violations; and cases in specific areas like bankruptcy, copyright, patent, and 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.

US Court of Appeals and District Court Map
Image Source: US Government

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, and preliminary felony hearings), county courts (larger jurisdiction; cases may relate to family law, probate law, and city ordinance violations), and state trial courts (largest jurisdiction; cases may relate to probate law, family law, property disputes, and 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 but instead relies 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 comprise the structure of the U.S. federal court system: 94 district courts, 13 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. As an example, legal parties filed 5,910 petitions in 2010, but the Supreme Court only granted certiorari to 165 cases — just 2.8% of cases. Cases most commonly heard by the Supreme Court include those dealing with an unusually significant legal principle, those where at least two federal courts differ in the interpretation of a law, and those dealing with interpreting the Constitution. Once the U.S. Supreme Court delivers a decision, it can only be overturned by a rarely granted request for a rehearing, a future Supreme Court ruling, or an amendment to the Constitution itself.

Corrections System in the United States

While law enforcement and the courts work to identify and intercept individuals involved in criminal activity, the corrections system serves a variety of simultaneous functions, such as keeping criminal populations separate, enacting punishments for wrongdoing, and promoting rehabilitation of wrongdoers. The U.S. corrections system stands alone as the largest system of its type in the world. Though home to less than 5% of the world’s population, the U.S. holds nearly 25% of the world’s prisoners — the highest global per capita rate of incarceration.

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.

Though home to less than 5% of the world’s population, the U.S. holds nearly 25% of the world’s prisoners — the highest global per capita rate of incarceration.

Incarceration entails the confinement of an individual in a prison, and daily prison life severely restricts an individual’s freedoms. In contrast, individuals 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 individuals violate the terms of their parole. A 2002 nationwide study showed nearly 68% of prisoners faced rearrest within three years of their release and 47% were ultimately reconvicted.

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 exists to govern 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?

Even after developing a foundational understanding of the goals and structure of each major component of the criminal justice system, the question remains: How does the criminal justice system work with so many moving pieces and independent parties involved? 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.

Though the process undertaken in every criminal justice case adheres to similar sets of rules and guidelines, specific steps in a case can vary based upon a number of factors, such as state versus federal jurisdiction, severity of a crime, whether a suspect faces juvenile or adult charges, and/or the prior criminal history of a suspect. The sections below offer a step-by-step look at the criminal justice process, starting with the act of committing a crime and ending with the completion of a corrections sentence.

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.

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.

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.

Careers in the Criminal Justice System

Criminal justice careers encompass many legal and law enforcement specializations, 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 a least a bachelor’s degree. However, many schools offer criminal justice degrees at multiple levels, including master’s and doctoral programs for individuals interested in higher-level management positions or university teaching opportunities. Criminal justice professionals tend to be detail oriented, inquisitive, highly organized, and possess a natural affinity for leadership and problem solving. The list below details a few popular criminal justice careers.

Correctional Officers and Bailiffs

Correctional officers supervise individuals in jail awaiting trial or serving sentences in prison. Bailiffs work as law enforcement officers within a courtroom where they maintain order, assist judges, and provide general courthouse security. Federal prisons generally require entry-level correctional officers to possess a bachelor’s degree.

Median Annual Salary: $43,510
Projected Growth Rate: -7%


Lawyers conduct legal research and analysis, interpret legal concepts, and provide advice and representation during criminal or civil court cases and private legal disputes. Clients may include individuals, businesses, and government agencies. Individuals who want to become lawyers must earn a bachelor’s degree and a doctor of jurisprudence degree. They must also pass a state bar exam.

Median Annual Salary: $119,250
Projected Growth Rate: 8%


Sociologists study society and human behavior by examining the processes by which groups, cultures, and organizations interact. Criminologists serve as sociologists who specialize in the study of crime, including its causes and effects. Finding employment as a sociologist typically requires at least a master’s degree.

Median Annual Salary: $79,650
Projected Growth Rate: 1%

Police and Detectives

Police work to ensure public safety, patrol assigned areas, and respond to emergency and nonemergency calls. Detectives gather facts and evidence for criminal court cases. Although a high school diploma and police academy training may meet minimum job requirements, some departments prefer applicants with a college degree.

Median Annual Salary: $62,960
Projected Growth Rate: 7%


  • SCOTUS Case Summaries This site allows readers to quickly access important details related to recent Supreme Court cases. Students and professionals alike may find this page useful while conducting research.
  • YouTube – American Bar Association The criminal justice section of ABA brings together prosecutors, defenders, judges, and academics to address pressing issues. The section’s YouTube channel posts full-length discussions and lectures.
  • American Bar Resources A useful starting point for student research, ABA offers an extensive list of online resources in 14 categories, including academia, corrections, and bar associations