By definition, a jury is a body of citizens sworn to render a decision in a court of law. There are different types of juries, though, and different types of cases and procedures call for different jury panels.
For most people, the word “jury” will conjure an image of 12 individuals sitting in a courtroom, hearing testimony from witnesses being questioned by prosecutors and defense attorneys. This type of jury—which renders a verdict in a formal trial—is called a trial jury. Trial juries are also referred to as “petit” juries, and they may consist of anywhere from six to 12 people. Generally, trial juries must render unanimous verdicts, but certain cases only require majority decisions.
A grand jury, on the other hand, decides whether enough evidence exists to prosecute a suspect in a crime. Grand juries generally consist of 23 people, as opposed to the smaller size of a petit jury. Unlike a trial jury, a grand jury is allowed to be much more involved in the process; they have access to any evidence that they wish to view, whereas a trial jury may only see evidence the prosecution or defense wants it to see.
Another major difference between trial juries and grand juries is the finality of their decisions. Whereas the verdict a trial jury renders is final, a grand jury’s decision may only be the first step in the process for the case in question. A prosecutor may use a grand jury as a sort of “trial run” before taking a case to actual trial.