As its name suggests, a Grand Jury has a larger number of jurors. A regular trials has 6-12 people. A Grand Jury has 12-23 people.
State Grand Juries are usually chosen in the same manner standard jurors are selected. The U.S. Courts summons eligible citizens who can serve up to 18 months.
Grand Jury Purpose
A Grand Jury is used solely to determine whether criminal charges should be brought against a particular defendant. It is not used for civil matters (civil matters generally deal with contracts and cases dealing with negligent/wrongful acts).
Only the Prosecutor (or Assistant District Attorney) presents the matter to the Grand Jury. The Prosecutor represents either the state or the United States.
During the proceedings, the Prosecutor presents the case and accuses the Defendant of a crime. There is no judge, defense attorney, or defendant. Only the Prosecutor’s witnesses present testimony and there is no cross-examination. The Grand Jury does not determine the defendant’s guilt or innocence. Instead, the Grand Jury determines whether there is probable cause to charge the defendant with the crime.
Sometimes a Special Grand Jury investigates matters for investigators, not prosecutors, usually when organized crime or political corruption is suspected. This is different from the aforementioned Grand Jury.
Weight of Evidence
“Probable cause” is the legal weight in which to determine whether to bring charges against the defendant.
The U.S. District Court says that when the evidence convinces 12 or more Grand Jurors that the defendant committed the crime, probable cause is established.
States have their own definitions of probable cause. The definitions are mostly made by common law, which means they are defined by court decisions, not statutes.
Origin of the Grand Jury
The 5th Amendment of the U.S. Constitution reads, in Part:
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury…
This takes its roots from the Magna Carter and was to protect citizens from spiteful, political or unjustified prosecutions.
Updates to the U.S. Constitution
On July 28, 1868, Congress ratified the 14th Amendment. It, in part, provided citizens “equal protection under the law” and directed that no state shall deprive anyone “due process of law,” or “equal protection of the laws.”
The courts have interpreted that the due process of law requirement did not necessarily require a Grand Jury indictment.
The states and the District of Columbia use Grand Juries, mostly for cases that may result in serious felony charges. Connecticut and Pennsylvania have eliminated them for criminal indictments, but still use them to investigate criminal activity.
For standard criminal cases, states conduct preliminary hearings. The prosecutor presents the case and the defendant may cross-examine. The judge then determines whether there is enough evidence for the defendant to stand trial. As with Grand Juries, the judge usually uses the “probable cause” standard.
The U.S. District Courts still use Grand Juries