When a criminal trial ends without a verdict, the court declares a mistrial. This procedural mechanism can be triggered by jury deadlock, serious procedural errors, or misconduct by a party. Mistrials leave the defendant in a state of legal limbo—neither convicted nor acquitted. Understanding what happens next requires careful analysis of the intersection between mistrial law and the constitutional protection against double jeopardy. This article explores the circumstances under which a mistrial occurs, the complex rules governing retrial, and the practical implications for defendants, prosecutors, and the justice system.

A mistrial is a trial that the judge invalidates before a verdict is reached, effectively nullifying the proceedings. The trial stops immediately, and no judgment is entered. However, unlike a dismissal with prejudice, a mistrial does not automatically bar the government from retrying the case. The trial court has broad discretion to declare a mistrial, but that discretion is cabined by the defendant’s constitutional rights.

Hung Jury (Jury Deadlock)

By far the most common cause of a mistrial is a deadlocked jury—often called a “hung jury.” After extensive deliberations, if the jury cannot reach a unanimous verdict on any charge, the judge may declare a mistrial. The judge typically gives an instruction encouraging further deliberation before accepting the deadlock. If the jury remains unable to agree, the trial ends without a verdict. In federal court, a mistrial due to hung jury is a classic example of a “manifest necessity” situation, which has important double jeopardy implications (discussed below).

Procedural Errors and Evidentiary Missteps

A trial may also be aborted because of legal errors that prejudice the defendant’s right to a fair trial. Examples include the introduction of inadmissible evidence, improper prosecutorial argument, failure to disclose exculpatory evidence, or violation of the defendant’s right to counsel. If the error is so fundamental that it cannot be cured by a curative instruction, the judge may grant a mistrial—often at the defendant’s request.

Prosecutorial or Judicial Misconduct

Misconduct by the prosecutor or even the judge can also lead to a mistrial. For instance, a prosecutor who intentionally references a suppressed confession, or a judge who makes prejudicial remarks in front of the jury, may force the court to abort the trial. In some cases, the misconduct is so egregious that retrial is later barred on double jeopardy grounds.

Other Grounds: Death of a Juror, Illness, Natural Disaster

Mistrials can also arise from purely logistical circumstances: the death or incapacitation of a juror or an attorney, a medical emergency involving the defendant, or a natural disaster that makes continuing the trial impossible. Courts evaluate such situations on a case-by-case basis, balancing the interests of justice against the defendant’s right to have the case decided by a particular jury.

Double Jeopardy and Mistrials: The Core Rules

The Fifth Amendment to the U.S. Constitution provides that no person shall “be subject for the same offence to be twice put in jeopardy of life or limb.” This protection, known as the rule against double jeopardy, usually attaches once the jury is sworn and impaneled. After jeopardy attaches, declaring a mistrial raises delicate constitutional questions about whether the defendant can be retried. The key variable is who caused the mistrial and why.

When Double Jeopardy Bars Retrial After a Mistrial

The general rule is that if a mistrial is granted over the defendant’s objection, the government may retry the defendant only if there was “manifest necessity” for the mistrial. This standard was established in the seminal case Perez v. United States (1824), in which the Supreme Court held that a trial court must exercise “sound discretion” and that retrial is allowed only when “the ends of public justice would otherwise be defeated.” In practice, manifest necessity is most clearly present when the jury is hopelessly deadlocked. Other examples include a juror’s sudden incapacitation or a courtroom fire. If the judge declares a mistrial without manifest necessity and the defendant objects, any subsequent prosecution violates double jeopardy.

Contrast that with the situation where the defendant consents to the mistrial. If the defendant moves for a mistrial or does not object to the judge’s declaration, double jeopardy generally does not bar retrial. The theory is that the defendant has voluntarily waived the right to have the trial completed by that jury. Courts routinely permit retrial after a defendant’s successful motion for a mistrial based on prosecutorial misconduct—provided the misconduct was not intended to provoke the defendant into moving for a mistrial.

Exceptions: When the Prosecutor Intentionally Provokes a Mistrial

An important exception arises when the prosecutor intentionally engages in conduct designed to goad the defendant into requesting a mistrial. In such a case, double jeopardy bars retrial. This rule was established in Oregon v. Kennedy (1982), where the Supreme Court held that retrial is prohibited if the prosecutor’s misconduct was intended to provoke the defendant into moving for a mistrial. The defendant must show that the prosecutor had the specific intent to cause a mistrial; mere negligent or even reckless misconduct is not enough.

Hung Jury: The Classic “Manifest Necessity” Scenario

As noted, a hung jury is almost always a sufficient ground for finding manifest necessity. The trial judge has broad discretion to find a genuine deadlock and declare a mistrial. Once declared, double jeopardy does not bar retrial—even if the defendant objects. In United States v. Sanford (1967), the Court reaffirmed that following a hung jury, the government is free to bring the defendant to trial again. This is the most common path to retrial after a mistrial.

Implications for the Defendant: Retrial, Dismissal, or Plea Bargain

For a defendant who has endured a mistrial, the future is uncertain. The prosecution may elect to retry the case, dismiss the charges, or offer a plea deal. The outcome depends on a range of factors, including the strength of the evidence, the cost and burden of a second trial, the nature of the mistrial, and public interest.

Refiling Charges and Speedy Trial Rights

If double jeopardy does not attach, the prosecution can refile the same charges. The defendant is entitled to a speedy trial, but the clock usually restarts once charges are refiled. In practice, judges may allow additional time because of the complexity of a second proceeding.

If the mistrial was caused by a procedural error, the prosecution may also choose to correct the defect and retry. For example, if evidence was excluded erroneously, the government may try to present it in a new trial. However, the prosecution must be cautious: if the first mistrial was due to prosecutorial overreach, the judge may later impose sanctions or even bar retrial on due process grounds.

Double Jeopardy Already Attached — Case Dismissed

In rare cases, the defendant may successfully argue that double jeopardy bars retrial altogether. This happens when the judge declared a mistrial without manifest necessity, over the defendant’s objection, and the government cannot justify the mistrial. The defendant can then file a motion to dismiss the indictment with prejudice. If granted, the case ends permanently. An appeal by the prosecution is possible but often unsuccessful.

Plea Offers After Mistrial

Often, after a mistrial, both sides reassess their positions. The defendant who “beat the case” in the first trial may feel emboldened, while the prosecution may be more willing to offer a favorable plea deal rather than risk another hung jury. Many mistrials result in negotiated resolutions rather than a second full trial.

Practical Observations: From the Courtroom to the Jury Room

Mistrials are not uncommon. According to data from the Bureau of Justice Statistics, about 2–5% of federal jury trials end in mistrials, with hung juries being the leading cause. State court rates vary widely. For legal professionals, understanding mistrial dynamics is essential for trial strategy.

The Judge’s Role: Deciding Whether to Declare a Mistrial

The trial judge must balance several competing interests: the defendant’s right to a fair trial, the public’s interest in finality, and judicial efficiency. When a jury reports deadlock, judges often read a modified Allen charge (encouraging further deliberation). If that fails, the judge polls the jury to confirm that further deliberation would be futile. Only then does the judge declare a mistrial.

In cases of error or misconduct, the judge must weigh whether a curative instruction can salvage the trial. If not, the judge will grant the defendant’s motion for mistrial. But the judge may also consider whether the error was so subtle that it didn’t prejudice the jury—in which case the trial continues.

Appeals and the Interplay with Double Jeopardy

If the defendant is convicted after a retrial following a mistrial, double jeopardy issues can still be raised on appeal. The appellate court will review the trial court’s determination of manifest necessity and whether the defendant consented. If the appeals court finds that retrial was barred, it will vacate the conviction and order dismissal with prejudice.

On the other hand, if the trial court grants a defendant’s motion to dismiss based on double jeopardy, the prosecution can immediately appeal under 18 U.S.C. § 3731. These interlocutory appeals are relatively common in high-profile cases.

Historical and Policy Context

The double jeopardy clause was a core part of the Founding Fathers’ vision of limited government power. The Supreme Court has consistently held that “the State with all its resources and power should not be allowed to make repeated attempts to convict an individual.” Write for the Court, Justice Black famously stated in Green v. United States (1957) that “the constitutional prohibition against double jeopardy protects an individual from being subjected to the hazards of trial and possible conviction more than once for an alleged offense.”

Mistrials, therefore, represent a tension between two values: the need to avoid endless litigation and the need to correct trial errors. The manifest necessity standard attempts to balance these values. Courts have repeatedly emphasized that the government should not be able to “shop” for a favorable jury by aborting trials that are going poorly, nor should defendants be able to force a reversal on trivial grounds to avoid a second trial.

Advice for Defendants and Attorneys

If you are facing a mistrial, or have been told that a mistrial was declared, consider the following steps:

  • Document the basis for the mistrial. If the mistrial was declared over your objection, your attorney should immediately file a motion to dismiss on double jeopardy grounds if there was no manifest necessity.
  • Evaluate the strength of the government’s case. A hung jury often suggests that the government’s proof was weak or that the jury found reasonable doubt. This can give you leverage in plea negotiations.
  • Beware of trigger-happy prosecutors. If the mistrial was caused by the prosecutor’s misconduct, explore whether the government’s actions were intended to provoke a mistrial. If so, double jeopardy bar may apply.
  • Consider motion practice before retrial. Your attorney may be able to exclude certain evidence or limit the charges based on what happened in the first trial.
  • Stay aware of the speedy trial clock. The government has a limited time to re-indict. If they fail to do so, you may be able to secure a dismissal based on speedy trial violations.

Conclusion

Mistrials are a complex but essential safety valve in the criminal justice system. Whether a mistrial ends the case forever or only delays the inevitable depends on a nuanced interplay of law, fact, and strategy. The double jeopardy clause provides powerful protection against governmental overreach, but its application to mistrials is far from absolute. For defendants, a mistrial may be a second chance, but it also invites a renewed legal battle. For prosecutors, it signals either a call to refine their case or an opportunity to reassess. In all cases, the principles of finality, fairness, and constitutional rights must be carefully balanced. By understanding the rules that govern mistrials and double jeopardy, both legal professionals and the public can better appreciate how the criminal trial process handles the rare occasion when a trial stops before justice is done.