The grand jury has long been used to investigate facts and accuse individuals and business entities of crimes. The Magna Carta, which King John granted to his subjects in 1215, recognized the role of the grand jury. Along with other English legal traditions, English Colonists brought the grand jury system to North America. Later, in 1787, the grand jury was incorporated into the Bill of Rights. The Fifth Amendment to the United States Constitution states that "[n]o person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury." This portion of the Fifth Amendment has been interpreted to mean that, unless this right is waived, an accused must first be indicted by a grand jury before the accused can be brought to trial on felony charges.

Federal grand juries are composed of between 16 and 23 individuals and are empanelled for a period of 18 months. Commonly, there is a foreperson, a deputy foreperson and a grand jury secretary. Under federal law, grand jury proceedings are secret; the only individuals other than the grand jurors permitted in the grand jury are federal prosecutors, witnesses and a court reporter.

Grand juries issue subpoenas to gather evidence and compel attendance of witnesses. Witnesses are not permitted to have their attorney present in the grand jury room but are permitted to consult with their attorney during recesses. Commonly, witnesses' attorneys remain just outside of the grand jury room for consultation. Grand jury witnesses should remain mindful that, even while testifying before a grand jury, they retain their Fifth Amendment right not to incriminate themselves.

After receiving evidence, a grand jury may deliberate as to whether to "hand down" an indictment. Unlike a trial, where the trial jurors are supposed to vote to convict only when they believe that the prosecution has proven its case "beyond a reasonable doubt," the grand jurors may vote to indict when they believe that there is "probable cause" to believe that a crime was committed and that the accused is the one who committed the crime. Also, unlike a trial, where a verdict must be unanimous, it only takes 12 grand jurors voting to indict for the indictment to issue. Thus, if there are 23 grand jurors present, an accused may be indicted if slightly more than half vote to indict.