The role of the jury during a trial is to decide what happened. Jurors listen to the testimony and examine the exhibits, weigh that evidence against the standard of proof the judge gives them, and return a verdict. The judge rules on the law; the jury rules on the facts. That division is written into the Sixth and Seventh Amendments, which guarantee a jury in criminal prosecutions and in civil suits over twenty dollars, and it is the reason verdicts in American courts are handed down by ordinary citizens rather than government officials.
The Jury as Trier of Fact
Once a jury is seated, the legal system calls it the “trier of fact.” In plain terms, the jury’s job is to figure out what actually happened. Did the defendant do what the prosecution claims? Did the plaintiff suffer the harm alleged? The judge handles every question of law: which evidence the jury is allowed to see, how the rules apply, and what legal standards govern the case. The judge is the referee who explains the rules. The jury watches the game and decides the score.
That split matters. The framers deliberately kept the power to convict or hold a party liable out of the hands of the one legal expert in the room. It belongs to the community, represented by the jurors. In a courtroom full of professionals, this is one of the few places where people with no legal training hold the deciding authority.
Weighing the Evidence
Throughout a trial, jurors hear witnesses, read documents, look at photographs, and sometimes handle physical objects admitted as exhibits. All of it has to be evaluated. When a witness testifies, jurors judge credibility by watching demeanor, considering potential biases, and noting whether the account holds up on cross-examination. Two witnesses can describe the same event in incompatible ways, and the jury decides whom to believe.
The strict rule is that the decision must rest only on evidence formally admitted in court. If the judge strikes testimony from the record, jurors are supposed to put it out of their minds. If a juror happens to know something about the case from outside the courtroom, that outside knowledge cannot factor in. You cannot look the defendant up online, drive past the scene on your way home, or ask a friend who happens to be an expert. Every piece of information the jury uses has to come through the courtroom’s front door.
The Standard of Proof the Jury Applies
The judge’s instructions tell jurors how sure they must be before ruling for one side. That threshold is called the standard of proof, and it changes with the type of case.
- Beyond a reasonable doubt is the criminal standard. The prosecution must leave jurors firmly convinced the defendant committed the crime. If a reasonable doubt remains, the jury must acquit. The bar is high because a conviction can take someone’s freedom.
- Preponderance of the evidence governs most civil cases. The plaintiff wins by showing their version is more likely true than not — the scales tipped just past fifty percent.
- Clear and convincing evidence is a middle standard used in matters like fraud claims, will contests, and withdrawal of life support. The evidence must make the claim highly probable, not merely more likely than not.
Jurors are also instructed to follow the law as the judge explains it, even if they personally disagree. The Ninth Circuit’s model instructions tell jurors they must apply the law “whether you agree with the law or not.” That instruction is standard across federal courtrooms, and it reinforces the line between the jury’s role as fact-finder and the legislature’s role as lawmaker.
Rules Jurors Must Follow During the Trial
The constraints on jurors are strict and courts enforce them. No independent research of any kind: no internet searches about the case, the parties, the lawyers, or legal terms. No visiting locations mentioned in testimony unless the judge arranges a formal viewing. No discussing the case with anyone outside the jury room, including family, until the trial is over. Even with other jurors, discussion is forbidden until formal deliberations begin with everyone present.
Breaking these rules is juror misconduct. A juror caught researching the case online can be removed and replaced with an alternate, and if the contamination has spread, the judge may declare a mistrial. Under federal law, a person who disregards a jury summons or violates the court’s orders can be fined up to $1,000, sentenced to up to three days in jail, or ordered to perform community service. More serious violations, such as communicating with a party to the case, can result in contempt charges.
Deliberation
After closing arguments and the judge’s final instructions, the jury is escorted to a private room. No one else is present. The first task is choosing a foreperson, who moderates the discussion and acts as the messenger between the jury and the court, sending any questions to the judge in writing. The title carries no extra vote or authority.
Deliberation itself is structured conversation. Jurors review the exhibits, talk through the testimony, and apply the legal standards the judge described. Disagreement is normal and expected. A juror who reads the evidence differently is supposed to explain the reasoning, not simply hold out and not simply fold under pressure. The quality of a verdict depends on whether the group actually debates the hard questions instead of rushing to agreement.
Reaching a Verdict
Unanimity and Jury Size
A federal criminal jury has 12 members, and every one of them must agree. The Supreme Court’s 2020 decision in Ramos v. Louisiana confirmed that unanimity applies in state criminal trials as well. A federal civil jury can have anywhere from 6 to 12 members, and the verdict must be unanimous unless both parties agree in advance to accept a non-unanimous result.
Hung Juries
When jurors cannot agree after extended deliberation, the result is a hung jury. Before declaring one, most judges try to break the deadlock. A common tool is the “Allen charge,” named after the 1896 Supreme Court case that approved it. The instruction urges jurors to reexamine their positions and give serious weight to each other’s views without abandoning honest convictions. Critics call it a “dynamite charge” because it can pressure holdouts into changing their votes just to end the process. If the jury is still deadlocked afterward, the judge declares a mistrial and the prosecution decides whether to retry the case with a new jury.
Announcing and Polling
When the jury reaches a decision, the foreperson notifies the court officer and everyone returns to the courtroom. The foreperson fills out the verdict form and announces the verdict in open court. Either side can then ask that the jury be polled, meaning each juror is individually asked whether they agree with the stated verdict. If the poll reveals that the vote was not actually unanimous, or does not meet whatever threshold the parties agreed to in a civil case, the judge can send the jury back to deliberate further or order a new trial.
Jury Nullification
One boundary is worth naming because jurors sometimes assume it is part of their role. Jury nullification happens when a jury returns a not-guilty verdict even though it believes the defendant broke the law, rejecting the law itself rather than the evidence. It has a long history, surfacing in cases where jurors view a law as unjust; during Prohibition, some juries refused to convict for alcohol offenses they considered victimless.
Nullification is technically possible because no one can punish a jury for its verdict, but it is not a recognized right. Courts treat it as inconsistent with the jury’s sworn duty to apply the law as instructed. Attorneys cannot argue for it, and judges do not tell jurors it exists. People who have handed out nullification pamphlets near courthouses have been charged with jury tampering. It is a power the jury possesses but is never officially told about, and the system actively discourages its use.