A mistrial is a judge’s order ending a trial before the jury reaches a verdict, which wipes the proceeding out without finding the defendant guilty or not guilty. Judges declare one when something has gone wrong seriously enough that the trial can no longer produce a fair outcome, a safeguard tied to the Sixth Amendment’s guarantee of an impartial jury.1Legal Information Institute. Sixth Amendment The case itself doesn’t vanish. In most situations the prosecution is free to start over with a new jury, so the defendant may have to go through the whole process again.
Why Judges Declare Mistrials
The most familiar trigger is a hung jury. Criminal convictions require a unanimous verdict under the Sixth Amendment, a rule the Supreme Court confirmed applies in every state in Ramos v. Louisiana.2Supreme Court of the United States. Ramos v Louisiana When jurors deliberate at length and still can’t agree, the foreperson tells the judge. The judge usually sends them back to keep trying, but if the deadlock clearly won’t break, the judge declares a mistrial.
Jury misconduct is another common cause. Jurors are supposed to decide the case on the evidence presented in court, nothing else. Doing independent research, visiting a crime scene, following news coverage, or discussing the case with outsiders all cross the line. When outside information has contaminated the panel and an alternate juror can’t cure the problem, a mistrial becomes the only option.
Lawyers and witnesses can also force a judge’s hand. A prosecutor may reference evidence the court already excluded, or a witness may blurt out something the jury was never meant to hear. The judge’s first move is usually to instruct jurors to disregard the statement, but some remarks are so damaging that no instruction can undo the harm.
Prosecutorial failure to turn over favorable evidence under the Brady doctrine can also end a trial early, with the judge choosing between a mistrial and barring the tainted evidence depending on how much damage has been done. And sometimes the problem is purely structural: a judge improperly admits evidence that tilts the jury unfairly, or a central participant like the judge, a key attorney, or an irreplaceable juror becomes seriously ill or dies during the proceedings.
How a Mistrial Gets Declared
Either side can ask for a mistrial by filing a motion. The attorney should raise it as soon as the problem surfaces, both to preserve the issue for appeal and to give the judge a chance to fix the error before it causes more harm. The motion has to explain why no jury instruction or lesser remedy can salvage a fair trial.
Judges can also declare a mistrial on their own initiative, without any attorney asking. That might happen after misconduct neither side has addressed, or when something like a juror’s medical emergency makes continuing impossible. The judge is ultimately responsible for the integrity of the proceedings regardless of what the lawyers choose to raise.
The Manifest Necessity Standard
When a mistrial is declared over the defendant’s objection, a higher bar applies. In United States v. Perez, the Supreme Court held that a court may discharge a jury without a verdict only when “there is a manifest necessity for the act, or the ends of public justice would otherwise be defeated.”3Library of Congress. United States v Perez, 22 US 579 (1824) This matters because if a judge declares a mistrial without manifest necessity and without the defendant’s consent, double jeopardy can block the prosecution from trying the case again. The judge is expected to consider less drastic alternatives first, such as replacing a problem juror with an alternate.
A hung jury is the clearest example of manifest necessity. Nobody caused the deadlock through misconduct, and there’s no realistic way to force agreement. A judge who ends a trial over a minor procedural issue that could have been corrected with an instruction, by contrast, risks having any retrial thrown out.
Can the Prosecution Retry the Case?
Usually, yes. The Fifth Amendment provides that no person shall “be subject for the same offence to be twice put in jeopardy of life or limb.”4Library of Congress. US Constitution – Fifth Amendment A mistrial, though, is not a verdict. Because no final judgment was reached on the merits, the Double Jeopardy Clause generally does not prevent a second trial. After a hung jury the prosecution is free to retry, since the jury simply couldn’t agree rather than acquitting. The same is true when the defense itself asked for the mistrial, since a defendant can’t engineer a do-over and then claim the Constitution forbids one.
The Narrow Exception That Blocks Retrial
There is one important exception. In Oregon v. Kennedy, the Supreme Court held that retrial is barred when the prosecution intentionally provoked the mistrial. The standard is specific: the misconduct must have been designed to goad the defense into asking for a mistrial so the prosecution could get a second shot at conviction.5Justia US Supreme Court. Oregon v Kennedy, 456 US 667 (1982) Sloppy or even reckless behavior isn’t enough. The defense has to show specific intent to trigger a mistrial for tactical advantage, and meeting that standard is difficult.
If the judge declared the mistrial over the defense’s objection, the manifest necessity analysis controls. If the prosecution can’t show the mistrial was genuinely necessary, the defendant walks free regardless of how strong the evidence looked.3Library of Congress. United States v Perez, 22 US 579 (1824)
What the Prosecution Does Next
After a mistrial, prosecutors generally have three realistic paths. Which one they take depends on what went wrong and how strong the case still looks.
- Retry the case with a new jury from scratch. This is common after a hung jury, especially when the split leaned toward conviction.
- Offer a plea bargain. If the first jury leaned toward acquittal, or a second trial would be expensive and uncertain, prosecutors may come back with a better deal to resolve things without another trial.
- Dismiss the charges. When key witnesses are no longer available, the evidence has weakened, or the first jury’s leanings suggest conviction is unlikely, prosecutors may drop the case. Dismissal is also more likely when the mistrial resulted from the prosecution’s own misconduct.
The Retrial Clock in Federal Cases
In federal court, the Speedy Trial Act puts a clock on the prosecution. A retrial must begin within 70 days of the date the mistrial becomes final.6Office of the Law Revision Counsel. 18 US Code 3161 – Time Limits and Exclusions Certain delays, such as time spent resolving pretrial motions, don’t count against that window. If the deadline passes without a retrial, the defendant can move to dismiss the charges. State courts have their own speedy trial rules, and the deadlines vary.
What a Mistrial Means for the Defendant
A mistrial doesn’t automatically release a defendant from custody or cancel their bail. The judge has discretion to keep existing conditions in place, modify them, or set new ones. Defendants who were free on bond during the first trial usually stay on the same bond, though the judge can adjust the amount. Defendants who were held in custody generally remain in custody unless they successfully seek release or modified bail at a later hearing.
The financial side is real. Attorneys who bill hourly charge separately for preparing and conducting a second trial, and even those who worked for a flat fee the first time typically treat a retrial as a new engagement with an additional fee. Transcript costs, expert witness fees, and lost income from additional time away from work all add up. For defendants with limited resources, the cost of a retrial can create pressure to accept a plea bargain even when the first jury’s deadlock suggested the prosecution’s case was weak.
Mistrials in Civil Cases
Everything above about double jeopardy applies only to criminal trials. The Fifth Amendment’s protection against being tried twice for the same offense has no role in civil litigation. When a civil trial ends in a mistrial, usually because of a hung jury or a serious procedural error, either party can start the case over without any constitutional barrier. The mechanics are the same: the judge declares the proceedings void, dismisses the jury, and schedules what comes next. The practical calculus is different, since both sides are paying their own costs, and that often pushes civil cases toward settlement rather than a second trial.