Petit Jury (Or Trial Jury) Meaning
A petit jury, also called a trial jury, is the group of jurors that decides disputed facts at a trial and returns a verdict under the judge’s instructions. The terms mean the same thing. A grand jury performs a different job: it considers whether there is a sufficient basis for a criminal charge, rather than deciding guilt at trial.
You may encounter “petit jury” on a jury-service notice, in a court’s explanation of a trial, or in a discussion of a verdict. The distinction matters because being considered for trial-jury service is different from being selected, and an indictment is different from a trial verdict. The U.S. Courts explanation of jury types distinguishes these roles in federal court.
What Does a Petit Jury Do at Trial?
Trial jurors have three connected tasks:
- Consider the evidence admitted in court. Jurors work from the trial record, including testimony and exhibits, rather than assembling their own evidence outside court.
- Decide what evidence to believe. Conflicting accounts require judgment about matters such as a witness’s opportunity to observe, memory, possible bias, and consistency with other evidence. Jurors may believe all, part, or none of a witness’s testimony; disagreement alone does not establish that someone lied.
- Apply the judge’s instructions and reach a verdict. The judge supplies the governing law. Jurors use those instructions to decide the factual issues submitted to them, rather than substituting their personal view of what the law should be.
The Ninth Circuit’s August 2026 model criminal instructions, Instructions 1.1 and 1.7, explain the fact-finding and credibility tasks. These are model instructions for that federal circuit; the instructions actually given in the particular trial control the jurors’ work.
An illustrative distinction: Two witnesses give different accounts of where a driver was standing. Trial jurors may compare the admitted photographs, testimony, and each witness’s opportunity to see. They should not visit the location themselves or search online for extra photographs to settle the disagreement. The federal Handbook for Trial Jurors, pages 11–12, explains the prohibition on outside research and the need to tell the court about outside information. The handbook is general guidance, not a replacement for the judge’s directions.
What Does the Verdict Decide in Civil and Criminal Cases?
In a criminal trial, the petit jury decides whether the prosecution has proved the charge. In federal court, the government must prove every element beyond a reasonable doubt. The defendant does not have to testify, produce evidence, or prove innocence. A not-guilty verdict means the prosecution did not establish guilt to the required standard; it does not require the jury to establish a different account of events. Ninth Circuit model Instruction 6.2 explains this burden and why the indictment itself is not evidence of guilt.
In a civil trial, the jury decides the factual issues submitted to it, which may include liability and damages in a claim for compensation. The U.S. Courts explanation gives preponderance of the evidence—more likely than not—as the ordinary civil comparison with the criminal standard. The applicable claim and the judge’s instructions determine the required proof; do not assume every civil issue uses the same burden.
“Petit jury” therefore identifies the decision-maker’s trial role. It does not tell you, by itself, whether the dispute is civil or criminal, which party will win, or whether every issue in the case will be decided by jurors.
Petit Jury vs. Grand Jury: Which Decision Is Being Made?
The following comparison concerns the federal system. State grand-jury procedures and uses can differ.
Question | Petit or trial jury | Grand jury |
|---|---|---|
What is its job? | Decide the factual issues at a civil or criminal trial. | Consider preliminary criminal matters and whether probable cause supports an indictment. |
How does evidence reach it? | Through the trial process, with the parties able to present and challenge evidence. A criminal defendant has no obligation to present a defense case. | Through a proceeding in which the prosecutor presents evidence; it is not the adversarial trial of guilt. |
What does its decision mean? | A criminal verdict addresses guilt under the trial standard; a civil verdict resolves the issues submitted. | An indictment is a formal accusation allowing a prosecution to proceed, not a guilty verdict. |
Does the same voting rule apply? | Federal criminal verdicts must be unanimous. Federal civil verdicts are unanimous unless the parties stipulate otherwise. | At least 12 grand jurors must concur in an indictment; unanimity of the entire 16–23-member body is not required. |
The U.S. Courts jury-types guidance explains the different purposes. Federal Criminal Rules 6(a), 6(f), and 31(a), together with Civil Rule 48(b), provide the membership and voting rules. An indictment reported in the news should therefore not be read as a finding that the accused committed the crime.
How Many People Serve, and Must They All Agree?
The answer depends on the court and case type. Under the current Federal Rules of Criminal Procedure:
- A federal criminal trial jury ordinarily has 12 members. Rule 23(b) permits a smaller jury through a written stipulation with court approval. After deliberations begin, the court can allow 11 jurors to return a verdict without such a stipulation when it finds good cause to excuse a juror.
- A federal criminal verdict must be unanimous. Rule 31(a) supplies that requirement. A smaller jury permitted under Rule 23 does not mean a majority vote is enough.
- Alternates are replacements, not extra verdict votes. Rule 24(c) allows up to six alternates. If an alternate replaces a juror after deliberations have begun, the court must instruct the jury to start deliberations again.
Under Federal Civil Rule 48, a civil jury must begin with six to twelve members. Each participates in the verdict unless excused under Rule 47(c). Unless the parties stipulate otherwise, the verdict must be unanimous and returned by at least six jurors. Saying that every federal civil jury has exactly six people is inaccurate.
State rules need their own check. For example, California Constitution Article I, section 16 allows three-fourths of the jury to render a verdict in a civil case. That state civil rule should not be imported into a federal criminal trial. These federal rules and the California provision were checked on October 27, 2026.
Quick Questions About Petit Juries
Does a jury panel mean the selected trial jury? Not necessarily. The federal trial-juror handbook uses “panel” for prospective jurors from whom a jury is selected. Questioning during selection, called voir dire, helps determine who will serve in the particular case. A summons or presence on a panel does not by itself establish that the person has been seated on that trial’s jury. Read the notice and follow the issuing court’s directions.
How do you pronounce “petit jury”? A common U.S. pronunciation is PET-ee JUR-ee: “petit” sounds like “petty.” Collins’ American-English entry gives the pronunciation of “petit” as ˈpɛti. This pronunciation does not identify a separate kind of trial jury.
Does every trial have a petit jury? No. A trial conducted before a judge without a jury is a nonjury or bench trial. Federal Criminal Rule 23 addresses jury waiver where the defendant is entitled to a jury: a written waiver, government consent, and court approval are required. Seeing “trial” in a document alone does not establish that a jury will decide it.