Grand jury vs. trial jury: What's the difference?
Understanding the two types of juries
The American legal system relies on two distinct types of juries that serve fundamentally different purposes. A grand jury determines whether enough evidence exists to formally charge someone with a crime. A trial jury (also called a petit jury) determines whether a defendant is actually guilty of the charges brought against them. Though both involve citizens evaluating evidence, the similarities largely end there.
Understanding these differences matters whether you've been summoned for jury duty, are following a high-profile legal case, or simply want to know how the justice system works. Each type of jury operates under different rules, different standards of proof, and different levels of secrecy.
| Feature | Grand Jury | Trial Jury (Petit Jury) |
|---|---|---|
| Primary purpose | Decides whether to charge (indict) someone | Decides guilt or liability |
| Number of jurors | 16 to 23 (federal); varies by state | 6 to 12 plus alternates |
| Standard of proof | Probable cause | Beyond a reasonable doubt (criminal); preponderance of evidence (civil) |
| Types of cases | Criminal only | Criminal and civil |
| Proceedings | Secret / closed | Generally public |
| Length of service | Up to 18 to 24 months | Duration of one trial |
| Verdict | Indictment ("true bill") or "no bill" | Guilty/not guilty or liable/not liable |
What is a grand jury?
A grand jury is a body of citizens assembled to review evidence presented by a prosecutor and determine whether there is probable cause to believe a person committed a crime. If the grand jury finds sufficient evidence, it issues an indictment, a formal criminal charge that sends the case to trial. If it does not, it issues what is known as a "no bill," and the case is dismissed for the time being.
| Grand Jury Characteristic | Details |
|---|---|
| Size | 16 to 23 jurors (federal); 9 to 23 depending on state |
| Standard of proof | Probable cause |
| Who presents evidence | Prosecutor only |
| Defense attorney present | No |
| Judge present | No (available if needed) |
| Proceedings open to public | No, entirely secret |
| Cases heard | Multiple cases over the term of service |
The role of the grand jury
Grand juries were originally conceived as a screening mechanism to protect citizens from unfounded criminal charges. The idea is straightforward: before the government can put someone on trial for a serious crime, a group of ordinary citizens must first agree that there is enough evidence to justify doing so.
The Fifth Amendment to the U.S. Constitution requires a grand jury indictment for federal felony charges. Many states also use grand juries, though the specific requirements vary. Some states allow prosecutors to file charges through a preliminary hearing before a judge instead.
How the grand jury process works
The prosecutor presents evidence by making statements, showing physical evidence, and calling witnesses to testify. Grand jurors may ask witnesses questions throughout the proceeding. However, there is no cross-examination, and the rules of evidence do not apply. This means evidence that could not be admitted at trial, such as hearsay or even illegally obtained evidence in some jurisdictions, can still be presented to the grand jury.
The accused person is typically not present unless called as a witness. Even if called to testify, the accused does not have the right to have an attorney present in the grand jury room in most jurisdictions.
An indictment is not a finding of guilt. It simply means the grand jury believes there is enough evidence to formally charge someone and proceed to trial. The defendant remains presumed innocent until proven guilty at trial.
What is a trial jury?
A trial jury, formally known as a petit jury, is the group of citizens that sits through an actual trial and renders a final verdict. In criminal cases, the trial jury decides whether the prosecution has proven the defendant's guilt beyond a reasonable doubt. In civil cases, it determines whether the plaintiff has shown by a preponderance of the evidence that the defendant caused them harm.
| Trial Jury Characteristic | Details |
|---|---|
| Size | 6 to 12 jurors plus alternates |
| Standard of proof (criminal) | Beyond a reasonable doubt |
| Standard of proof (civil) | Preponderance of the evidence |
| Who presents evidence | Both prosecution/plaintiff and defense |
| Defense attorney present | Yes |
| Judge present | Yes, presides over trial |
| Proceedings open to public | Yes (deliberations are private) |
| Cases heard | One case per juror |
The role of the trial jury
The trial jury serves as the ultimate fact-finder in the American legal system. Jurors hear evidence from both sides, listen to witness testimony subject to cross-examination, receive legal instructions from the judge, and then deliberate in private to reach a verdict.
In criminal cases, the stakes are high because a person's liberty is on the line. This is why the standard of proof, beyond a reasonable doubt, is the highest standard in the legal system. In civil cases, where the dispute typically involves money or other remedies rather than imprisonment, the standard is lower: the plaintiff must show it is more likely than not that the defendant caused harm.
How the trial jury process works
Trial jurors are selected through a process called voir dire, during which attorneys from both sides question potential jurors to identify any biases or conflicts of interest. Once seated, jurors hear opening statements, witness testimony, cross-examination, and closing arguments from both the prosecution (or plaintiff) and the defense.
After all evidence is presented and the judge delivers legal instructions, the jury retires to deliberate in private. The jury must then reach a verdict. In federal criminal cases and most state criminal cases, the verdict must be unanimous. Once the verdict is delivered, the jurors are discharged.
Key differences between grand juries and trial juries
While both types of juries involve citizens reviewing evidence, the differences between them are substantial. They differ in purpose, size, procedure, transparency, and the standard of proof required to reach a decision.
| Factor | Grand Jury | Trial Jury |
|---|---|---|
| Purpose | Determine if charges should be filed | Determine guilt or liability |
| Stage of proceedings | Pre-trial (before charges are filed) | During trial (after charges are filed) |
| Jury size | 16 to 23 (federal) | 6 to 12 plus alternates |
| Standard of proof | Probable cause | Beyond a reasonable doubt / preponderance of evidence |
| Evidence heard from | Prosecution only | Both sides |
| Cross-examination | Not permitted | Required |
| Rules of evidence | Do not apply | Strictly enforced |
| Secrecy | Entirely secret | Public trial; private deliberations |
| Judge present | No | Yes |
| Defense attorney present | No | Yes |
| Outcome | Indictment or no bill | Verdict (guilty/not guilty or liable/not liable) |
| Number of cases | Multiple cases over months | One case |
| Vote required | Majority (varies by jurisdiction) | Typically unanimous in criminal cases |
How proceedings differ
The procedural differences between grand jury and trial jury proceedings are among the most striking distinctions. Grand jury proceedings are one-sided and secret, while trials are adversarial and public.
| Procedural Element | Grand Jury | Trial Jury |
|---|---|---|
| Public access | Closed to the public | Open to the public |
| Sides represented | Prosecution only | Both prosecution and defense |
| Witness cross-examination | No | Yes |
| Evidentiary rules | Relaxed | Strict |
| Record of proceedings | Sealed unless court orders release | Public record |
Why grand jury proceedings are secret
Grand jury secrecy serves several important purposes. It encourages witnesses to testify fully and honestly without fear of public retaliation. It allows grand jurors to make decisions free from outside pressure or interference. Most importantly, it protects the reputation of individuals who are investigated but never indicted.
Everyone present in the grand jury room, including the prosecutor, court reporter, and jurors themselves, is prohibited from disclosing what occurs during proceedings. Violations can result in contempt of court charges.
The adversarial nature of trials
Trials operate under a completely different philosophy. The adversarial system ensures that both the prosecution and defense have the opportunity to present evidence, call witnesses, and challenge the other side's case through cross-examination. A judge presides over the proceedings to enforce rules of evidence and ensure fairness.
This two-sided process is why the trial jury's verdict carries so much more weight than a grand jury indictment. The trial jury has heard the full picture from both parties before reaching its conclusion.
Jury selection and qualifications
Both grand jurors and trial jurors are drawn from the same pool of eligible citizens in a given jurisdiction. The basic qualifications are generally the same, though the screening process differs significantly.
| Qualification | Details |
|---|---|
| Citizenship | Must be a United States citizen |
| Age | Must be at least 18 years old |
| Residency | Must reside in the jurisdiction where summoned |
| Language | Must understand and communicate in English |
| Criminal record | Must not have been convicted of a felony (with some exceptions) |
Trial jurors go through voir dire, an extensive screening process where attorneys question potential jurors about their backgrounds, beliefs, and potential biases. Both sides can challenge jurors they believe cannot be impartial.
Grand jurors, by contrast, are typically not screened for bias or other potential issues in the same way. Since the grand jury only hears from one side and is not making a final determination of guilt, the selection process is less rigorous.
Length of service
The time commitment required for grand jury and trial jury service is dramatically different. This is one of the most practical distinctions for citizens who receive a jury summons.
| Service Aspect | Grand Jury | Trial Jury |
|---|---|---|
| Typical term | Up to 18 months (extendable to 24 months) | Duration of one trial (days to weeks, occasionally months) |
| Frequency of meetings | 1 to 2 days per week or every other week | Every day the trial is in session |
| Number of cases | Multiple cases throughout the term | One case only |
| Schedule flexibility | Set schedule over months | Continuous until verdict |
Grand jurors do not typically meet every day. In smaller districts, a grand jury might convene only one day every other week. In larger districts with significant criminal caseloads, grand jurors may meet a couple of days each week. Over the course of their term, they review multiple cases.
Trial jurors, on the other hand, serve every day the trial is in session until a verdict is reached or the case is otherwise resolved. Once the trial concludes, they are discharged and their service is complete.
Powers and limitations of each jury
Each type of jury wields significant but carefully limited power within the justice system. Understanding what each jury can and cannot do helps clarify their respective roles.
| Power or Limitation | Grand Jury | Trial Jury |
|---|---|---|
| Can issue criminal charges | Yes (indictment) | No |
| Can determine guilt | No | Yes |
| Can impose sentences | No | No (judge determines sentencing in most cases) |
| Can subpoena witnesses | Yes | No (attorneys and judges issue subpoenas) |
| Can ask questions of witnesses | Yes | Limited (varies by jurisdiction) |
| Can investigate independently | Yes, to a degree | No |
Grand jury powers
Grand juries have the power to issue indictments on criminal charges, typically felonies. They can also issue subpoenas to compel witnesses to testify and produce documents. In some cases, grand juries have investigative authority that extends beyond the specific cases brought to them by prosecutors.
However, the grand jury does not have the power to decide whether a prosecutor moves forward with a case after indictment, whether a defendant is ultimately convicted, or what punishment should be imposed.
Trial jury powers
The trial jury's power lies in its ability to render a final verdict. In criminal cases, this means deciding whether the defendant is guilty or not guilty. In civil cases, this means determining liability and, often, the amount of damages to be awarded.
Trial juries generally do not determine sentences in criminal cases. Sentencing is typically the responsibility of the judge, though some states allow jury sentencing in certain circumstances. Sentences may include imprisonment, probation, criminal fines, or community service.
If a grand jury declines to indict, the case is dismissed for the time being. However, the prosecutor is not permanently barred from seeking an indictment through a new grand jury later, particularly if stronger evidence emerges. An acquittal by a trial jury, on the other hand, is final due to double jeopardy protections.
Frequently asked questions
Can you refuse grand jury service?
Jury service, whether for a grand jury or trial jury, is a legal obligation. Ignoring a jury notice can result in civil and criminal penalties, including fines and potential contempt of court charges. Certain exemptions and deferrals may be available depending on your jurisdiction, such as medical hardship or extreme financial burden.
Are jurors compensated for their service?
Yes, both grand jurors and trial jurors receive compensation, though the amount varies by jurisdiction. In many states, jurors receive around $40 to $50 per day of service. Federal jurors are paid $50 per day, increasing to $60 per day after 10 days of service. Some employers are required to continue paying employees during jury service.
| Juror Compensation | Daily Rate |
|---|---|
| State jurors (typical range) | $40 to $50 per day |
| Federal jurors (first 10 days) | $50 per day |
| Federal jurors (after 10 days) | $60 per day |
Can you serve on both a grand jury and a trial jury?
Yes, it is possible to serve on both types of juries at different times. However, you would not serve on both simultaneously. A person who served on a grand jury that indicted a defendant would not be eligible to serve on the trial jury for that same case.
Do all states use grand juries?
No. While the Fifth Amendment requires grand jury indictments for federal felony cases, this requirement has not been incorporated against the states. About half of U.S. states require grand jury indictments for certain serious crimes. Other states use preliminary hearings before a judge as an alternative, or give prosecutors the option of filing charges directly through an information.
What happens after a grand jury indictment?
After an indictment, the defendant is formally charged and the case moves toward trial. The defendant will be arraigned, meaning they appear before a judge, are informed of the charges, and enter a plea. An attorney will be appointed if the defendant does not already have one. The court will set bail or bond conditions, and the case will proceed through the pre-trial and trial phases.
How often do grand juries indict?
Grand juries indict in the vast majority of cases presented to them. Federal grand juries return indictments in over 99% of cases. This high rate has led to criticism that grand juries serve more as a rubber stamp for prosecutors than as an independent screening body. Because only the prosecution presents evidence, the process inherently favors indictment.