How the Jury System Works: Selection, Deliberation, and Verdict

What Is the Jury System?

The jury system is a fundamental feature of the American legal system in which a group of ordinary citizens — not a judge — decides questions of fact in a trial. The Sixth Amendment guarantees the right to a jury trial in criminal cases; the Seventh Amendment preserves it in most civil cases involving more than $20 at common law.

The principle behind jury trials is democratic: important decisions about liberty and civil disputes should be made by a cross-section of the community, not by government officials alone.

Types of Juries

Trial Jury (Petit Jury)

The familiar 12-person jury that decides guilt in criminal cases or liability in civil cases. In criminal cases, the jury applies the law as instructed by the judge to determine whether the prosecution has proven guilt beyond a reasonable doubt. In civil cases, it determines whether the plaintiff has proven their case by a preponderance of the evidence (more likely than not).

Grand Jury

A grand jury (typically 16–23 members) doesn't decide guilt — it decides whether the government has enough evidence to bring criminal charges. If the grand jury agrees there is probable cause, it issues an indictment. Grand jury proceedings are secret, and the target of the investigation has no right to present evidence or have an attorney present.

The Fifth Amendment requires grand jury indictment for serious federal crimes, but most states allow prosecutors to file charges directly (via information) without a grand jury.

Jury Selection (Voir Dire)

Jurors are selected through a process called voir dire (French for "to speak the truth") — questioning of prospective jurors by attorneys and sometimes the judge to uncover biases that might prevent fair judgment.

Attorneys use two types of challenges to exclude jurors:

• Challenges for cause: Unlimited. Used when a prospective juror cannot be impartial — they know the defendant, have relevant financial interests, or have already formed a firm opinion about the case. Requires the judge's approval.
• Peremptory challenges: Limited (typically 3–10 per side). Allows attorneys to exclude jurors without stating a reason. However, peremptory challenges cannot be used to discriminate on the basis of race or sex (Batson v. Kentucky).

The Trial Process

Once a jury is seated, the trial proceeds:

1. Opening statements: Each attorney outlines what they expect the evidence to show
2. Prosecution/Plaintiff's case: Direct examination of witnesses and presentation of evidence
3. Cross-examination: The opposing attorney challenges witnesses
4. Defense case: Defense presents its evidence and witnesses
5. Closing arguments: Each attorney summarizes the evidence and argues for their client
6. Jury instructions: The judge explains the law the jury must apply
7. Deliberation: The jury deliberates in private

Deliberation and Verdict

Jury deliberations are secret — only the jurors are present. The jury first elects a foreperson to lead discussion. Jurors review the evidence, apply the judge's legal instructions, and discuss until they reach a verdict.

In federal criminal cases and most state criminal cases, a unanimous verdict is required for conviction. (Two states — Oregon and Louisiana — historically allowed non-unanimous criminal verdicts, but the Supreme Court ruled in Ramos v. Louisiana (2020) that unanimity is constitutionally required.)

In civil cases, most states allow verdicts by a supermajority (e.g., 10 of 12 jurors). If a jury cannot agree, a hung jury results — the judge declares a mistrial, and the case may be retried.

Jury Nullification

Jury nullification occurs when a jury acquits a defendant despite believing they technically violated the law — because the jury believes the law is unjust, the punishment is too severe, or prosecution is unwarranted in this case. Jury nullification is controversial: the courts do not recognize it as a right, and judges may dismiss jurors who explicitly state they intend to nullify, but jurors have no obligation to explain a not-guilty verdict.

Jury Duty: Rights and Obligations

Jury service is a civic obligation. All eligible citizens (U.S. citizen, 18+, no disqualifying criminal conviction, able to understand English) may be summoned. Failure to appear for jury duty can result in contempt of court fines.

Federal law prohibits employers from firing employees for serving on a jury. Most states also provide job protection for jurors, though only some states require employers to pay wages during jury service.