An indictment, an information, and a criminal complaint are charging instruments that set forth criminal charges against a defendant and the basis for probable cause to believe the defendant committed a crime.

If a grand jury decides the evidence presented establishes probable cause, it issues an indictment against the accused. In federal criminal prosecutions, at least 12 jurors must vote to indict. The indictment is called a true bill. If the grand jury does not find sufficient probable cause, it returns a no bill.

In a misdemeanor case—or in a felony case where the accused has waived indictment and has agreed to plead guilty—the matter is not presented to the grand jury. In those instances, an information, which is a document outlining probable cause, is filed with the federal district court.

And a criminal complaint is often filed when prosecutors want to make an arrest quickly because a crime is about to occur, or has just occurred. In such a situation prosecutors may not have time to use the grand jury process and will instead file a written criminal complaint, together with an affidavit signed by a government agent familiar with the case. A judge or magistrate judge will then review the complaint and affidavit and issue an arrest warrant if the judge finds probable cause. After an arrest is made based on a criminal complaint, federal law requires the defendant be charged by an indictment—or by a criminal information if it is a misdemeanor case or a felony case where the accused has waived indictment and has agreed to plead guilty—within 30 days.

In state criminal prosecutions, the use of an indictment, information, or complaint as the charging instrument varies from state to state. The requirements and circumstances for such charging instruments are generally located in a state’s statutes—often in the penal or criminal code, or the code of criminal procedure.

In Massachusetts, an indictment, information, and criminal complaint are all used as charging instruments to formally accuse an individual of a crime. An indictment is issued by a grand jury when it finds probable cause that the accused committed a crime, and it is necessary for felony charges unless the defendant waives the right to a grand jury. For less serious offenses, such as misdemeanors, or in felony cases where the accused agrees to plead guilty, an information may be filed instead. This is a formal accusation made by a prosecutor without a grand jury. A criminal complaint is typically used for making swift arrests when a crime is imminent or has just occurred, and it is accompanied by an affidavit to establish probable cause. A judge reviews the complaint and can issue an arrest warrant. Under federal law, after an arrest based on a criminal complaint, the defendant must be charged by an indictment or information within 30 days. The specific procedures and requirements for these charging instruments in Massachusetts are detailed in the state's General Laws, particularly within the penal code and the code of criminal procedure.