A jury is a group of ordinary citizens pulled from the community to hear evidence in a court case and decide the outcome. In a criminal trial, the jury decides whether the defendant is guilty. In a civil trial, it decides whether one party is legally responsible for harming another. Asking what a jury is really means asking two things at once: who these people are, and what power they hold once they sit down in the jury box. The short answer to both is that they are peers of the parties, and their decision is the decision of the case.
The Two Kinds of Juries
Most people picture one kind of jury, but the legal system actually uses two, and they do very different jobs.
Trial Juries
A trial jury, sometimes called a petit jury, is the group that sits through a trial from start to finish. It has six to twelve members. They hear witness testimony, review physical evidence, listen to arguments from both sides, and then deliver a verdict. In a criminal case, that means deciding whether the prosecution has proved guilt beyond a reasonable doubt. In a civil case, it means deciding whether the plaintiff has shown it is more likely than not that the defendant caused the harm claimed.1United States Courts. Types of Juries
Grand Juries
A grand jury does not decide guilt. It sits at the very beginning of a criminal case and decides whether prosecutors have enough evidence to formally charge someone with a crime at all. A grand jury has sixteen to twenty-three members, meets in private, and hears only from the prosecution. If it finds probable cause, it issues an indictment and the case moves toward trial. If it does not, the charges stop there.1United States Courts. Types of Juries The Fifth Amendment requires this step for serious federal crimes, which is why grand juries exist in the first place: they’re meant to be a check on prosecutors bringing weak cases.2Constitution Annotated. Amdt5.2.2 Grand Jury Clause Doctrine and Practice Grand jurors can serve for a month or longer, sometimes up to a year, depending on how complex the investigation is.
Why Juries Exist
Three amendments in the Bill of Rights give juries their place in American courts. The Fifth Amendment requires a grand jury before serious federal charges can proceed.2Constitution Annotated. Amdt5.2.2 Grand Jury Clause Doctrine and Practice The Sixth Amendment guarantees anyone accused of a crime carrying more than six months of potential imprisonment the right to have a jury decide guilt or innocence.3Constitution Annotated. Amdt6.4.3.2 Right to Trial by Jury Generally The Seventh Amendment preserves the right to a jury in federal civil lawsuits where the amount in dispute exceeds twenty dollars.4Congress.gov. U.S. Constitution – Seventh Amendment The common thread is a simple principle: important legal outcomes should rest with a group of peers, not with a single government official.
Who Serves on a Jury
Federal law sets the baseline for who can sit on a federal jury. You have to be a U.S. citizen, at least eighteen, able to read, write, and understand English, and you must have lived in the judicial district for at least a year. A person charged with or convicted of a felony whose civil rights have not been restored is disqualified.5Office of the Law Revision Counsel. 28 USC 1865 – Qualifications for Jury Service Beyond the hard rules, courts allow certain groups, including people over seventy in many districts, to request a permanent excuse, and they consider hardship requests for medical, caregiving, or financial reasons.6United States Courts. Juror Qualifications, Exemptions and Excuses
Names come primarily from voter registration rolls, supplemented in many districts by driver’s license and state ID records so the pool reflects a fair cross-section of the community.7Office of the Law Revision Counsel. 28 USC 1863 – Plan for Random Jury Selection From that list, people are randomly summoned to the courthouse.
Voir Dire
Getting summoned does not mean you serve. Once a group of prospective jurors arrives, the judge and attorneys question them in a process called voir dire. The questions are meant to surface bias, personal connections to the case, or anything else that would keep someone from being fair.8Legal Information Institute. Federal Rules of Criminal Procedure Rule 24 – Trial Jurors
Attorneys can remove prospective jurors in two ways. A challenge for cause asks the judge to dismiss someone who has shown a clear inability to be impartial, like a close relationship to one of the parties. There is no limit on these, but the judge has to agree the reason is valid. A peremptory challenge lets an attorney dismiss a juror without giving any reason. Each side gets a set number of these.
Peremptory challenges have one firm limit. In Batson v. Kentucky, the Supreme Court held that attorneys cannot strike jurors because of race. If the other side suspects a racially motivated strike, the striking attorney must offer a race-neutral reason, and the judge decides whether that reason is genuine or a pretext.9Justia U.S. Supreme Court. Batson v. Kentucky, 476 U.S. 79 (1986) Courts later extended the same protection to gender.
What the Jury Does During Trial
Jurors listen to opening statements, witness testimony, cross-examinations, and closing arguments. They examine the physical evidence, which can include documents, photographs, or forensic reports. They are expected to keep an open mind and avoid forming conclusions until they have heard everything.
Before deliberations, the judge delivers jury instructions explaining the law that applies to the case and the standard of proof the jury has to use. In a criminal case, that standard is proof beyond a reasonable doubt. In a civil case, it is a preponderance of the evidence, meaning the plaintiff’s version is more likely true than not. Jurors are required to follow those legal standards rather than their personal sense of what feels right.
In longer trials, the court often seats up to six alternate jurors who watch the proceedings alongside the regular panel. If a juror falls ill, has a family emergency, or is removed for misconduct, an alternate takes their seat with the same authority. If an alternate steps in after deliberations have already started, the judge instructs the jury to start its discussions over from the beginning.10Office of the Law Revision Counsel. Federal Rules of Criminal Procedure Rule 24 – Trial Jurors
How a Jury Reaches a Verdict
After closing arguments and instructions, the jury moves to a private room to deliberate. Members talk through the evidence, work through disagreements, and try to reach a verdict. In federal criminal cases, and in state criminal cases for serious offenses, every juror has to agree. The Supreme Court confirmed this unanimity rule in Ramos v. Louisiana in 2020, holding that the Sixth Amendment requires every juror to agree before a defendant can be convicted.11Supreme Court of the United States. Ramos v. Louisiana, 590 U.S. 83 (2020) Civil cases often allow non-unanimous verdicts, depending on the jurisdiction. When the jury has decided, the foreperson announces the verdict in open court.
When the Jury Can’t Agree
Sometimes a jury cannot reach a unanimous verdict no matter how long it deliberates. That is called a hung jury, and it produces a mistrial. The case is not over. Prosecutors can retry it with a new jury, and doing so does not violate double jeopardy because no verdict was ever reached. Judges often try to avoid a mistrial first by issuing an Allen charge, named for an 1896 Supreme Court decision, which asks jurors to reexamine their positions and keep deliberating while still following their individual conscience. Critics argue these instructions pressure holdouts, and several states have banned them.
When There Is No Jury
The right to a jury trial is a right, not a requirement. A criminal defendant can waive it and ask a judge to decide the case alone in what’s called a bench trial. Some defendants prefer that when the evidence is technical or when they think a judge will be more objective than a group of strangers. In civil cases, a party has to affirmatively demand a jury within the deadline set by the rules, or the right is waived by default.12Legal Information Institute. Federal Rules of Civil Procedure Rule 38 – Right to a Jury Trial; Demand A case without a jury is still a trial. It just means one person, the judge, is doing the work that twelve would otherwise share.