Preliminary Hearing

Preliminary hearings play a variety of roles in the criminal system. Despite the prosecutors' high success rate in establishing probable cause, the hearings may force the government to engage in self-screening before presenting the case, which helps ensure that innocent defendants are not required to endure the trauma of a trial. There are limits, however, on how stringent a screen the preliminary hearing can be. The lax evidentiary rules, the reluctance to usurp the trial jury by making credibility determinations, and the prosecutor's ability in many jurisdictions to circumvent the hearing by obtaining an indictment may constrain the magistrate's ability to dismiss all but the very weakest cases.

The high likelihood of a bindover also means, however, that many defense counsels will choose not to call witnesses or otherwise raise a defense for fear of revealing their evidence or strategy, and thus defendants will often either waive the hearing or attempt to extract other benefits from the proceeding. The chance to see the prosecutor's evidence and to lay the foundation for future impeachment through the cross-examination can play an important role in preparing the defense for trial or plea negotiations.