In a federal grand jury, a prosecutor collects evidence through subpoenas and search warrants and then presents it — mostly through live witness testimony — in a closed room where no judge and no defense attorney are present. The grand jurors do not decide guilt. They decide only whether there is probable cause to believe a crime occurred and that a specific person committed it.1United States Courts. Handbook for Federal Grand Jurors If at least 12 jurors agree that standard is met, they return an indictment and the case moves toward trial.
How the Prosecutor Gathers Evidence
The prosecutor runs the investigation. Federal agents do the fieldwork, but the prosecutor chooses which leads to pursue and which evidence eventually reaches the grand jury. Two tools do most of the work.
A subpoena ad testificandum orders a person to appear and testify under oath. A subpoena duces tecum orders a person or organization to produce specific items: financial records, emails, photographs, contracts, phone records, anything relevant to the investigation. Both carry the force of a court order.
Search warrants let law enforcement enter a specific location and seize evidence. Warrants require a judge’s advance approval based on probable cause, so before agents ever knock on a door, the prosecutor has already convinced a judge that evidence of a crime is likely to be found there. Subpoenas do not need that same up-front judicial approval, which is one reason they carry so much of the investigative load.
Who Is in the Room
Federal Rule of Criminal Procedure 6(d) is strict about who may be present while the grand jury sits: government attorneys, the witness being questioned, interpreters if needed, and a court reporter or recording operator.2Legal Information Institute. Federal Rules of Criminal Procedure Rule 6 – Section: (d) Who May Be Present No judge. No defense attorney. The person under investigation has no right to be there, no right to cross-examine, and often no right to know the proceeding is happening at all. This is not an adversarial hearing. It is a one-sided screening of the government’s case.
How the Evidence Is Presented
The prosecutor calls witnesses one at a time. Each takes an oath and answers the prosecutor’s questions. The grand jurors themselves can ask follow-up questions, usually by writing them out and passing them to the prosecutor.1United States Courts. Handbook for Federal Grand Jurors That is a meaningful difference from trial, where jurors sit silent.
The formal rules of evidence do not fully apply. Hearsay is admissible. Secondhand accounts are admissible. An FBI agent can summarize what other witnesses told them rather than parading each of those people through the room. The Supreme Court confirmed this in Costello v. United States, holding that an indictment built entirely on hearsay is still valid.3Justia. Costello v United States, 350 US 359 (1956) The practical effect is that prosecutors have wide latitude in what they choose to put in front of the grand jury and how they choose to package it.
Why the Presentation Is One-Sided
A prosecutor has no legal duty to show the grand jury evidence pointing toward innocence. The Supreme Court decided this in United States v. Williams, ruling that imposing an exculpatory-evidence requirement on prosecutors “would be incompatible with this system” and that courts lack authority to impose one.4Legal Information Institute. United States v Williams, 504 US 36 (1992)
Department of Justice policy encourages prosecutors to present “substantial evidence” that directly negates guilt when they know about it, but that guidance is internal, not enforceable. If a prosecutor withholds favorable evidence, the indictment still stands. That structural imbalance is what people are pointing at when they say a grand jury will indict a ham sandwich.
What Witnesses Can Do During Testimony
Any witness can invoke the Fifth Amendment and refuse to answer a question that might incriminate them.5U.S. Congress. General Protections Against Self-Incrimination Doctrine and Practice The privilege has to be invoked question by question — you cannot refuse to appear or announce a blanket refusal to say anything. A court can override the invocation only when it is “perfectly clear” that no truthful answer could possibly be incriminating.
Although a defense lawyer cannot sit inside the grand jury room, a witness has the right to step out and consult with counsel before answering. The DOJ’s standard Advice of Rights form spells this out, telling witnesses they will be given “a reasonable opportunity to step outside the grand jury room to consult with counsel.”6U.S. Department of Justice. Justice Manual 9-11.000 – Grand Jury For anyone called to testify, having a lawyer in the hallway is the only real-time protection the process offers.
When a witness invokes the Fifth and the government wants the testimony anyway, prosecutors can obtain a court order granting immunity under 18 U.S.C. § 6002. Once the order issues, the witness can no longer refuse on self-incrimination grounds.7Office of the Law Revision Counsel. 18 USC 6002 – Immunity of Witnesses What the witness gets in return is use immunity: nothing they say, and no evidence derived from what they say, can be used against them in a later prosecution, except in a perjury case.
Use immunity is narrower than transactional immunity. The government can still prosecute the same person for the same crime if it can prove its evidence came from sources entirely independent of the compelled testimony. The Supreme Court upheld this arrangement in Kastigar v. United States, placing the burden squarely on the prosecution to show independent sources.8Justia. Kastigar v United States, 406 US 441 (1972)
What Happens If a Witness Refuses
Refusing to comply with a grand jury subpoena carries real consequences. A federal court can punish disobedience of any lawful court order, including a subpoena, by fine, imprisonment, or both under 18 U.S.C. § 401.9Office of the Law Revision Counsel. 18 USC 401 – Power of Court
For a witness who refuses to testify or produce documents without a valid legal reason, the federal recalcitrant witness statute allows civil confinement for up to 18 months, and never longer than the remaining life of the grand jury’s term.10Office of the Law Revision Counsel. 28 USC 1826 – Recalcitrant Witnesses The confinement is meant to coerce, not to punish. Agree to testify and you walk out. Refuse and you sit.
How the Grand Jury Decides
When the prosecutor finishes, everyone else leaves. The jurors deliberate alone, without the prosecutor, the court reporter, or any outside guidance. A federal grand jury has between 16 and 23 members, and a vote of at least 12 is required to return an indictment.11Legal Information Institute. Federal Rules of Criminal Procedure Rule 6 – Section: (a) Summoning a Grand Jury
Twelve votes produces a “true bill” — the indictment. Fewer than 12 produces a “no bill,” meaning the grand jury declined to charge. A no bill is not an acquittal and does not bar the government from trying again. DOJ policy requires the responsible U.S. Attorney to approve any resubmission to another grand jury, but no legal rule prevents it.6U.S. Department of Justice. Justice Manual 9-11.000 – Grand Jury
An indictment is a formal accusation, not a verdict. It moves the case toward arraignment and, eventually, a trial where the government must prove guilt beyond a reasonable doubt and the defendant finally gets to put on a defense.