Generally, a preliminary hearing is where a judge decides whether there's enough evidence to make you stand trial on the charges filed against you. The judge's decision at a preliminary hearing is like the decision a grand jury makes in deciding whether to return an indictment against you.
The prosecution must establish "probable cause" of two things: that a crime was committed and that you committed it. "Probable cause" is a low standard of proof. Think of it like "reason to believe." It doesn't rise anywhere near the level of "proof beyond a reasonable doubt" or even "preponderance of the evidence," which is the standard used in civil cases.
The rules of evidence are relaxed at preliminary hearings. Hearsay is allowed, and evidence may be used against you regardless of whether was legally collected or "seized."
Preliminary hearings are used in cases in which the prosecutor files the charges without going through the grand jury. If the grand jury reviews the case and returns an indictment, the "probable cause" determination is made by the grand jury, and no preliminary hearing is necessary.
In most states, it's at the "arraignment," not the preliminary hearing, that a person enters a plea of guilty or not guilty. In some states and counties, the arraignment happens immediately after the preliminary hearing. In others, the arraignment is scheduled for a future date.
You're permitted to waive a preliminary hearing, and it's fairly common to do so. If you waive the hearing, you're not pleading guilty; you're just admitting that probable cause exists to make you stand trial on the charges. The waiver is sometimes accomplished by filling out a form in court. Oral questioning by the judge to make sure you understand you're giving up the right to have the hearing may also do it.
You should discuss any decision on whether to have or waive a preliminary hearing with a qualified criminal defense attorney.
An arraignment is a court hearing at which you enter a plea of guilty or not guilty to the charges that have been filed against you. If you're contesting the charges, your plea will be not guilty.
Assuming you've been granted bail after your arrest, it's unlikely bail will be revoked or cancelled at your arraignment. Bail usually continues through trial or a guilty plea, and in most places through sentencing.
But it's possible the prosecutor may ask the judge to either increase or revoke your bail:
- If you violate the terms of your bond or commit another crime while on bail
- If the government receives information that you intend to flee before trial or that you lied about your prior criminal history in your bail application
- If more serious charges are filed against you while you're waiting for trial
In most, if not all, cases, you or your lawyer will be notice notice of the prosecutor's intent to ask that your bail be increased or revoked. This gives you a fair chance to challenge the request at a hearing before any action is taken on your bond.