Washington - Grand juries play a central role in the American justice system. They are tasked with listening to evidence presented by prosecutors and witnesses and then deciding, by a secret vote, whether there's enough evidence to charge a person with a felony, which is any criminal offense punishable by at least one year in prison.
Grand juries are required in federal felony prosecutions, and many U.S. states have adopted a similar system. However, in some states, prosecutors can also present their evidence to a judge, who then decides whether someone can be charged with a crime.
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Federal grand juries are made up of 16 to 23 members. At least 12 jurors must agree before an indictment - a formal charge - can be brought against someone. Grand jurors are selected from the same pool of ordinary citizens who serve as trial jurors. They are identified from public records such as driver's licenses and voting registries. Grand jurors serve from 18 to 36 months, usually meeting a few times a month, and have the power to question witnesses and issue subpoenas.
"The grand jury system is important in terms of deciding who's going to face criminal charges, but it's also important for involving citizens in the criminal justice system," said Peter Joy, a law professor at Washington University in St. Louis. "The origins of the grand jury system are based on, in a sense, a certain degree of trying to keep the government honest."
Grand juries were originally conceived as a safeguard against government power, which is why the Founding Fathers wrote them into the U.S. Constitution. But former federal prosecutor Green isn't convinced the so-called "people's panel" fulfills that function in a meaningful way.
"If the original idea of the Founding Fathers was, as I believe it was, to be a restraint on government power ... it's probably not a very effective tool to protect people from prosecution overreaching," Green says. "And there's a pretty significant risk that, if the prosecutor gets it in their head that somebody's guilty, they can achieve an indictment whether the person is guilty or not."
Grand juries rarely decline to indict. In 2010, government statistics showed that federal grand juries brought charges more than 99% of the time.
While the grand jury might be a rubber stamp in most cases, the panel is more likely to play a meaningful role in cases that draw widespread public attention, Joy says.
"I think it's very likely that prosecutors in presenting the evidence to the grand jury most likely tried to present more evidence than they might in a typical type of case and presented in a way that would be balanced," he says.
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Some states require prosecutors to show evidence that the accused might be innocent. However, federal prosecutors are not required to do so.
"The higher the profile the accused has, the greater the likelihood is that the prosecutor really wants to feel that he or she has a solid case, and they're going to want to test out the evidence in a way that would give them increasing confidence in the case that they have," Joy says.
"Because the stakes are high, a smart prosecutor - if there is some contrary evidence that might put into question guilt or innocence - they're likely to use the grand jury as a vetting [testing] process for that."