What Is a Grand Jury? Indictments, Secrecy, and the Role in Criminal Justice

What Is a Grand Jury?

A grand jury is a panel of citizens — typically 16 to 23 members in federal cases — that reviews evidence presented by a prosecutor to determine whether there is sufficient probable cause to formally charge a person with a serious crime. The grand jury does not decide guilt or innocence; it merely acts as a screening mechanism to filter out cases where the evidence is too weak to justify putting someone through a full criminal trial.

The name grand jury distinguishes it from a petit (or trial) jury, which is the smaller jury that actually hears evidence at trial and renders a verdict. The grand jury system has deep roots in English common law and was included in the Fifth Amendment to the U.S. Constitution, which states that no person shall be held for a capital or otherwise infamous crime unless on a presentment or indictment of a Grand Jury.

Grand Jury vs. Trial Jury

The differences between a grand jury and a trial jury are significant. A trial jury typically consists of 6 to 12 jurors who hear evidence from both the prosecution and defense, apply legal standards of proof beyond a reasonable doubt, and return a verdict of guilty or not guilty. The entire process is public and governed by strict rules of evidence.

A grand jury, by contrast, hears only the prosecution's evidence. The target of the investigation has no right to appear, no right to have an attorney present inside the grand jury room, and no right to confront or cross-examine witnesses. The standard applied is not proof beyond a reasonable doubt but the much lower bar of probable cause — a reasonable belief that a crime was committed and that the accused committed it. Rules of evidence are significantly relaxed, meaning hearsay and other evidence inadmissible at trial can be presented to a grand jury.

Secret Proceedings and Why They Matter

Grand jury proceedings are conducted in strict secrecy. Grand jurors are sworn to secrecy, and witnesses may not disclose their testimony without court permission. Prosecutors and court personnel involved in the proceedings are similarly bound. This secrecy serves several purposes: it protects the reputation of suspects who may ultimately not be charged; it prevents targets from fleeing or destroying evidence; it encourages witnesses to testify candidly without fear of retaliation; and it protects the integrity of the investigation.

The secrecy rule has important exceptions. A witness may discuss their own testimony, and courts can order disclosure in certain circumstances, such as when grand jury materials are needed in a subsequent trial. Federal Rule of Criminal Procedure 6(e) governs the secrecy requirements in federal cases and specifies the limited circumstances under which grand jury materials can be disclosed.

Indictment vs. Information

When a grand jury finds sufficient evidence, it returns a true bill, which becomes a formal criminal indictment. If it finds insufficient evidence, it returns a no bill and the charges are dropped — at least temporarily. A prosecutor may bring the case back to a new grand jury if new evidence emerges.

An information is an alternative charging document that bypasses the grand jury entirely. A prosecutor files an information directly with the court based on a finding of probable cause at a preliminary hearing before a judge. Many states allow felony prosecutions by information with the defendant's consent, or in cases where the defendant waives their right to a grand jury indictment. In federal court, the Fifth Amendment guarantees the right to a grand jury indictment for serious federal crimes, making informations largely unavailable in federal felony prosecutions.

Federal vs. State Grand Juries

The Fifth Amendment's grand jury requirement applies only to federal prosecutions. The Supreme Court has never incorporated this right against the states through the Fourteenth Amendment, meaning states are free to structure their charging systems as they see fit. As a result, practice varies significantly by state. About half of states require grand jury indictments for serious felony charges; others allow prosecutors to file charges by information after a preliminary hearing; a handful have abolished grand juries for most purposes entirely.

Federal grand juries are empowered to investigate federal crimes across a wide range, from white-collar fraud and public corruption to narcotics trafficking and terrorism. Federal grand juries also have subpoena power — the ability to compel witnesses to testify and to require the production of documents. This investigative authority makes the grand jury a powerful tool for complex, long-running investigations where investigators need to gather evidence from reluctant witnesses or institutions.

The Fifth Amendment and the Right Against Self-Incrimination

The Fifth Amendment not only establishes the grand jury right but also protects witnesses from being compelled to incriminate themselves. A witness called before a grand jury may invoke the Fifth Amendment and refuse to answer questions that might tend to incriminate them. Prosecutors can overcome this by granting immunity — either use immunity (protecting the witness from having their specific testimony used against them) or transactional immunity (protecting the witness from prosecution for the entire transaction under investigation). Once immunity is granted, the witness must testify or face contempt of court.

Critics of the grand jury system argue that it has become a rubber stamp for prosecutors, who control what evidence is presented and how witnesses are questioned. The phrase often attributed to former New York Chief Judge Sol Wachtler — that a grand jury would indict a ham sandwich if a prosecutor asked — captures this critique. Defenders counter that the grand jury's secrecy and investigative powers remain essential tools for complex prosecutions and that the institution still serves as a meaningful check on prosecutorial overreach in at least some cases.