American prosecutors have extensive discretion over whether to charge, what to charge and how many charges to bring against an arrestee. However, most prosecutors dismiss charges against a substantial percentage of arrestees at an early point in the process because:

• the arrestee's conduct did not constitute a crime;
• while there was a crime, it is too insignificant to prosecute;
• while there was a crime, it is not provable against this person at this point; and
• while there was a crime, the prosecutor believes that pre-trial diversion to a treatment or other program is the most appropriate disposition.

Until the trial begins, the prosecutor may voluntarily dismiss the charges against the accused without prejudice, and thus can bring the same charges at a later date. The Sixth Amendment provides that there shall be no criminal prosecution except upon indictment by a grand jury. However, the Supreme Court has held that this is one of the few rights included in the Bill of Rights that is not binding on the states. Thus, each state can decide for itself whether to use a grand jury to initiate the formal criminal proceeding.

The accused must be arraigned and formally charged within a short period of time. At arraignment, the judge reads the formal charges and with respect to each charge, asks the defendant to plead guilty, not guilty or not guilty by reason of insanity. Most states also permit a plea of nolo contendere (no contest) which, for practical purposes, is equivalent to a guilty plea. A plea of not guilty can subsequently be changed to a plea of guilty. Only in limited circumstances can a guilty plea be withdrawn.