Plea bargaining in the United States is very common; the vast majority of criminal cases in the United States are settled by plea bargain rather than by a jury trial. They have also been increasing in frequency—they rose from 84% of federal cases in 1984 to 94% by 2001. The same  ratio is at the state level, and more recent statistics, say the numbers are more like 97%, on both the state and federal level.

Plea bargains are subject to the approval of the court, and different States and jurisdictions have different rules. Game theory has been used to analyze the plea bargaining decision.

The constitutionality of plea bargaining and its legal footing were established by Brady v. United States (1970). The U.S. Supreme Court warned, in the same decision, that this was conditional only and required appropriate safeguards and usage—namely that plea incentives so large or coercive as to overrule defendants’ abilities to act freely, or used in a manner giving rise to a significant number of innocent people pleading guilty, might be prohibited or lead to concerns over constitutionality. Previously, the Court had held in United States v. Jackson that a law was unconstitutional that had the effect of imposing undue fear in a defendant (in that case, the fear of death) to the point it discouraged the exercise of a constitutional right (the 6th Amendment covering the right to a jury trial), and also forced the defendant to act as an unwilling witness against himself in violation of the 5th amendment. The Court stated that:

The plea is more than an admission of past conduct; it is the defendant’s consent that judgment of conviction may be entered without a trial, a waiver of his right to trial before a jury or a judge. Waivers of constitutional rights not only must be voluntary but must be knowing, intelligent acts done with sufficient awareness of the relevant circumstances and likely consequences.

Most Americans are under the mistaken impression that when the government accuses someone of a crime, the case typically proceeds to trial, where a jury of laypeople hears arguments from the prosecution and the defense, then deliberates over the evidence before deciding on the defendant’s guilt or innocence.

This image of American justice is wildly off the mark. Criminal cases rarely go to trial, because about 95 percent are resolved by plea bargains. In a plea bargain, the prosecutor usually offers a reduced prison sentence if the defendant agrees to waive his right to a jury trial and admit guilt in a summary proceeding before a judge.

In today’s criminal justice system, convictions come by agreement, or plea bargain. The tradition of being tried by one’s peers,  established by the Sixth Amendment to the U.S. Constitution has all but disappeared. The plea bargain has made jury trials obsolete.

This standard operating procedure was not contemplated by the Framers. The inability to enter into plea arrangements was not among the grievances set forth in the Declaration of Independence. Plea bargaining was not discussed at the Constitutional Convention or during ratification debates. In fact, the Constitution says “the Trial of all Crimes, except in Cases of Impeachment; shall be by Jury.” It is evident that jury trials were supposed to play a central role in the administration of American criminal justice. But as the Yale law Professor John Langbein noted in a 1992 Harvard Journal of Law and Public Policy article, “There is an astonishing discrepancy between what the constitutional texts promise and what the criminal justice system delivers.”

No one ever proposed a radical restructuring of the criminal justice system, one that would replace jury trials with a supposedly superior system of charge-and-sentence bargaining. Like the growth of government in general, plea bargaining slowly crept into and eventually grew to dominate the system.

From a defendant’s perspective, plea bargaining extorts guilty pleas. People who have never been prosecuted may think there is no way they would plead guilty to a crime they did not commit. But when the government has a “witness” who is willing to lie, and your own attorney urges you to accept one year in prison rather than risk a ten-year sentence, the decision becomes harder. As William Young, then chief judge of the U.S. District Court in Massachusetts, observed in an unusually blunt 2004 opinion, “The focus of our entire criminal justice system has shifted away from trials and juries and adjudication to a massive system of sentence bargaining that is heavily rigged against the accused.”