How does the grand jury process work and who presents evidence to grand jurors?
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Executive summary
The grand jury is a secret, investigatory body that decides whether prosecutors have shown probable cause to bring formal criminal charges; it operates differently from a trial jury and its proceedings are typically ex parte with only the government presenting evidence [1] [2]. Prosecutors—usually the U.S. Attorney or Assistant U.S. Attorneys in federal matters—drive the process: they select witnesses, present documentary exhibits and advise jurors on the law while federal or state agents gather investigative material for that presentation [3] [2] [4].
1. What the grand jury’s job actually is
A grand jury’s constitutional and statutory function is to determine whether evidence establishes probable cause to indict, not to adjudicate guilt, and it can both investigate and issue indictments or presentments for crimes triable in the jurisdiction [1] [5]. Grand juries may sit for extended periods and investigate broadly, including issuing subpoenas to compel testimony or documents, and their deliberations and votes are secret under the rules [2] [6] [5].
2. Who collects and brings the evidence into the room
Investigative work is typically done by law‑enforcement agents—FBI, IRS, state police—who gather reports, records and witness interviews; those materials are evaluated and packaged by prosecutors, who actually present them to the grand jurors [2] [4]. Prosecutors often rely on agents to explain technical or investigative results, but it is the government attorney who decides what to present, which witnesses to call, and how to frame the legal theory for jurors [3] [7].
3. How evidence is presented and who speaks in the room
Grand jury sessions are not adversarial: prosecutors open the matter, call witnesses to testify under oath, and introduce documentary exhibits; no defense counsel is normally present and the target of the investigation rarely speaks unless subpoenaed [8] [9]. Prosecutors also instruct jurors on the applicable law and may use copies of original documents as exhibits while preserving originals according to Department of Justice guidance [4] [8].
4. Limits, secrecy, and recordkeeping
The Federal Rules and Justice Department guidance impose secrecy on proceedings and strict handling of grand jury materials; transcripts or recordings are kept confidential and access is tightly limited, although records may be reviewed by courts in certain circumstances such as when an indictment is returned [2] [10]. Prosecutors are expected not to present evidence obtained in violation of constitutional rights and the identifying and marking of grand jury materials is governed by internal protocols to protect both confidentiality and evidentiary integrity [4] [11].
5. Where prosecutorial discretion and criticism meet
Because prosecutors control which matters are presented, which witnesses appear, and which evidence is shown, critics argue the grand jury can be tilted toward indictments and used to extend prosecutorial reach when evidence is thin; defenders stress the grand jury’s subpoena power and independent capacity to request witnesses or additional documents as checks on that power [6] [12]. The official materials acknowledge the prosecutor’s duty to be fair and to advise jurors of the law, yet also warn prosecutors not to present evidence known to be tainted by clear constitutional violations [4] [11].
6. Practical differences across jurisdictions and remaining questions
State rules vary—quorum sizes, the presence of clerks or other officials, and whether hearsay or automatic immunity rules apply differ by state—so the federal model is a baseline not a universal template [13] [14] [12]. Reporting and handbooks explain the mechanics and the central role of prosecutors and agents, but public materials do not reveal the full content of any particular grand jury’s evidence, so assessments of fairness or balance in specific cases depend on records or court review rather than the sealed proceedings themselves [7] [10].