Plea bargaining refers to the negotiations between prosecutors and defense lawyers on how to resolve criminal charges. Plea bargaining results in defendants' pleading guilty or nolo contendere (a plea in which the defendant does not contest the charges, but which carries the same primary consequences as a guilty plea) in return for a stated sentence, agreement not to request more than a certain sentence, or dropped charges. Judges are sometimes part of the negotiation process as well.
The vast majority of cases are settled by plea bargaining, which can begin as soon as charges are filed and continue right up to the jury's verdict.
A bargain has the obvious advantages of certainty and reduction of risk. The defendant avoids the risk that:
From the prosecutor's point of view, a settled case will clear the trial calendar, leaving room for other cases. It also removes the risk that the defense will convince the jury to acquit or hang. Settled cases result in happy judges, too, because their case loads lessen—prosecutors always benefit when they make judges happy.
A defendant who pleads guilty must admit guilt. This person loses the chance to convince the trier of fact, be it a judge or jury, of his lack of guilt. The most seasoned trial attorneys, be they prosecutors or defense attorneys, will be hesitant to tell you that a case is a slam-dunk for conviction. Juries are unpredictable, as are witnesses.
Prosecutors lose a bit, too, when they bargain a case. Victims and the public may be angered at a settlement for a crime they think deserves the full force of the prosecutor's efforts. And when the deal does not include a specified, agreed-upon sentence, the prosecutor may end up unpleasantly surprised when the judge hands down a lenient punishment.
Not every case can be bargained "down." In some instances, where the statute provides for a mandatory minimum sentence, the prosecutor cannot agree to a lighter sentence. For example, statutes proscribing driving under the influence of drugs or alcohol often specify that increased penalties will apply for repeat offenders; and certain assault crimes carry an enhanced sentence when the victim was a child or other protected person. In these situations, the prosecutor may be able to reduce the charges (to reckless driving or a lesser assault, for example). But, without reducing the charges, the prosecutor wouldn't be able to promise a lighter sentence than the minimum specified for the original charge.
Plea bargaining that attempts to nail down a specific sentence must involve a willing judge for the bargain to be a deal that the defendant can rely on. That's because the sentencing function is uniquely judicial—no prosecutor can authoritatively tell the judge, "This is what the defense and I have agreed will be the sentence." Sometimes, the bargaining will involve the judge from the outset, and when that happens and the judge signs-off on the deal, the sentence is set. But often the deal will involve only a promise that the prosecutor will not ask for a sentence greater than a certain amount. In these cases, there's no guarantee that the judge will follow this recommendation. To protect themselves in these scenarios, defendants often build into the plea the option to withdraw the plea if the judge indicates that he or she will impose a sentence other than the one recommended by the prosecutor. (For more, see Withdrawing a Guilty Plea.)
Defendants who plead guilty in exchange for a lesser charge or sentence must still appear before a judge and admit guilt. Judges will conduct an often lengthy "voir dire" (oral examination) of the defendant, asking whether the defendant understands that he or she is giving up the right to trial, to testify, and to call witnesses. The voir dire includes asking defendants if they understand every element of the offense to which they intend to plea, and if they admit each such element. Judges will not accept a guilty plea unless a genuine "Yes" follows each of the judge's questions. Judges conduct these examinations in order to make sure that defendants are well aware of what they are giving up—and in order to ensure that later, a defendant cannot claim that he pleaded in ignorance of the rights that were never explained to him.
Because a plea won't "go down" unless the defendant passes the judge's voir dire, attorneys typically spend a time preparing their clients for this examination. Defendants who are pleading guilty out of expediency, but who resist admitting actual guilt, will have a hard time successfully pleading before a rigorous judge.