Unless waived by the accused, every federal felony case must be indicted by a grand jury. In addition, the state of New York uses grand juries. Grand juries are not used for misdemeanors.
Grand jury proceedings are conducted in secret. During the proceedings, a prosecutor presents the evidence against the accused. If the grand jury finds there is probable cause, an indictment is returned. If probable cause is found lacking, the case is dismissed.
The accused does not have a right to testify before the grand jury, but many prosecutors are happy to allow the accused to testify. There is no right to counsel in the grand jury room. The accused must be placed under oath and the prosecutor can examine him or her about anything relevant to the alleged crime that was committed. Therefore, it can be difficult to protect the accused in front of a grand jury, and most criminal attorneys do not wish for their clients to testify in front of a grand jury except in special circumstances.
There is currently a lot of criticism in the legal community of the grand jury system. Grand jurors usually are not screened for bias and aren’t given instructions on the law. The prosecutor does not have to present any exculpatory evidence in favor of the accused. Witnesses don’t have a right to a lawyer, which can be problematic.