Probable cause is a standard set forth in the Fourth Amendment of the U.S. Constitution and means that a reasonable person would believe that a crime had been committed. It is substantially less strict than the threshold of beyond a reasonable doubt, which is used to convict someone during a criminal trial.
Where a jury in a criminal trial must reach a unanimous verdict, a grand jury can issue an indictment with a simple majority.
Indictments may be sealed until the suspect appears in court. Prosecutors share their evidence with defense attorneys, who often ask a judge to dismiss the case on various legal grounds.
A trial may not be scheduled for months — or years — after an indictment is handed down.