Every case that goes to court within the federal criminal justice system first goes before the grand jury. The main job of this group is to decide if the prosecutor has enough evidence to bring charges against you.
It is common for people to confuse a grand jury with other types of juries. They are not the same and have completely different functions.
The prosecutor will bring cases for crimes that carry a year or more in prison before the grand jury. Lesser crimes do not go before the jury and go straight into the system.
The grand jury will look over evidence and information the prosecutor presents in a case. The jury does not have the duty to determine guilt or innocence. They only have to decide if the information the prosecutor presents is enough to allow for a criminal charge. The defense has no role in this process since there are no arguments or determination of the actual guilt of the accused person.
Hand down an indictment
If the jury decides the prosecutor has enough evidence for a case, they will hand down an indictment. The indictment is the formal charge. It will allow a judge to issue a warrant for your arrest and begins the criminal process for you.
The grand jury has a lot of power. It is an important part of the criminal justice system because the jurors help to weed out cases that are not worth the time and money of the federal government to prosecute.