A mistrial is a criminal trial that ends without a verdict. The case isn't decided; the proceeding is terminated; and what happens next depends on why the trial ended. For defendants, family members, and people just trying to understand the process, the concept is often more confusing than it should be. The good news is that the rules are reasonably clear once you know them.
This guide explains what mistrials are, the most common reasons they happen in Missouri criminal courts, what happens after one is declared, and the strategic considerations both sides weigh in seeking or opposing one.
What a mistrial actually is
A mistrial is a judge's declaration that a criminal trial cannot proceed to a verdict. The trial is terminated; whatever proceedings have occurred up to that point are essentially nullified; and the case returns to a pre-trial posture. The defendant is not acquitted — that requires a not-guilty verdict. The defendant is not convicted either.
What happens after the mistrial declaration depends on:
• The reason for the mistrial.
• Whether the defendant requested it (or consented).
• Whether the prosecution was at fault for the cause.
• Constitutional double-jeopardy considerations.
In most cases, the prosecution can retry the defendant. In some cases, the prosecution is barred from retrial. The distinction matters enormously.
The most common reasons for mistrial
1. Hung jury
The most common cause. After deliberation, the jury cannot reach the unanimous verdict required for criminal cases (Missouri requires unanimity in criminal trials). The judge polls the jurors, confirms they are deadlocked beyond reasonable hope of progress, and declares a mistrial.
Hung-jury mistrials usually allow retrial. Prosecutors then decide whether to retry, accept a plea to a lesser charge, or dismiss. The defense's negotiating leverage often increases after a hung jury — the prosecution has now learned its case has weaknesses.
2. Juror misconduct
A juror discusses the case with someone outside the proceeding, conducts independent research (Googles the defendant, visits the crime scene), is exposed to inadmissible information, or otherwise violates the court's instructions. If discovered before deliberations, the juror may be replaced with an alternate. If discovered after deliberations begin or there are no alternates available, mistrial may be required.
3. Prosecutorial misconduct
The prosecutor introduces inadmissible evidence, improperly comments on the defendant's silence (constitutional violation under Doyle v. Ohio), references a prior conviction the defense was not informed about, or otherwise prejudices the jury so severely that no curative instruction can fix it.
Prosecutorial-misconduct mistrials are particularly significant because they sometimes implicate double-jeopardy. If the misconduct was intentional and intended to provoke a mistrial, retrial may be barred under Oregon v. Kennedy.
4. Defense misconduct or witness disclosure
Less common but possible. Defense counsel violates the court's evidentiary rulings, the defendant testifies to matters that the court had ruled inadmissible, or the defense calls a surprise witness whose testimony cannot be fairly addressed by the prosecution. Mistrials in these circumstances generally permit retrial.
5. Judicial error or unforeseen circumstances
The judge realizes she has made a significant evidentiary ruling that cannot be corrected, the courthouse experiences an emergency that disrupts proceedings, key witnesses become unavailable mid-trial, or a juror's medical emergency leaves the jury below the required number.
6. Manifest necessity
The catch-all category. Some unforeseen event makes continuation impossible — severe weather closing the courthouse, a witness's death, a defendant's medical emergency, a legitimate but unanticipated due-process problem.
Double jeopardy and retrial
The Fifth Amendment's double-jeopardy clause prohibits successive prosecutions for the same offense after acquittal or conviction. A mistrial is neither — so the question is whether double-jeopardy bars retrial after this particular mistrial.
The general rule: retrial is permitted when:
• The defendant requested or consented to the mistrial.
• The mistrial was declared due to "manifest necessity" without the prosecution's fault.
• The mistrial was due to a hung jury.
• The mistrial was based on prejudicial error not caused by the prosecution.
The general rule: retrial is barred when:
• The mistrial was caused by intentional prosecutorial misconduct designed to provoke a mistrial (Oregon v. Kennedy, 456 U.S. 667).
• The defendant did not request or consent to the mistrial and there was no manifest necessity.
• A trial judge declares a mistrial without giving the defense an opportunity to be heard.
Each of these categories has Missouri case law refining how it applies in specific circumstances.
What happens after a Missouri mistrial
The case returns to a pre-trial posture. The judge sets new dates for the next trial. The defendant's bond status remains as it was — defendants on bond stay on bond; defendants in custody typically stay in custody.
The interim period (often weeks or months) allows for:
Renewed plea negotiations. Both sides have learned new information from the first trial. The state's case may have shown weaknesses. The defense may have learned what evidence the prosecution cannot effectively present. Plea offers often shift after a mistrial.
New motions practice. Issues that emerged during the first trial sometimes support new pretrial motions for the second trial — motions in limine to exclude problematic evidence, suppression motions on issues that became visible during testimony, motions to dismiss for double-jeopardy or due-process violations.
Witness reassessment. Both sides reconsider which witnesses to call, how to prepare them, and what testimony to elicit. Witnesses whose first-trial performance was poor may be omitted in the second trial.
Jury-pool considerations. The pool for the second trial draws from the same county; some venirepersons may have heard about the first trial. Voir dire becomes more pointed.
The strategic considerations
Both sides weigh factors when seeking, opposing, or accepting a mistrial:
Prosecution incentives:
• Mistrials can favor the prosecution if the prosecution wasn't doing well in the first trial — a "do over" with refined witnesses and tactics.
• Hung-jury mistrials allow the prosecution to learn how the case played and adjust.
• Mistrials disadvantage the prosecution when the case was going well and key witnesses become harder to reproduce.
Defense incentives:
• Mistrials can favor the defense if the defense wasn't doing well — another shot with refined cross-examination and presentation.
• Defense should generally consent to mistrial only when there's a strong reason — the consent affects the double-jeopardy analysis.
• Defense should consider whether the prosecution is likely to retry, given the cost and witness challenges.
Mistrials are not failures
Defendants and families often view mistrials as bad outcomes — expecting an acquittal, getting an unfinished proceeding instead. The reality is more nuanced. A mistrial that ends a strong-prosecution case is often a defense win, particularly when the prosecution decides not to retry. A mistrial that ends a strong-defense case is often a defense loss, particularly when the prosecution is now better-prepared.
The honest evaluation depends on what the case looked like at the moment of mistrial, what each side learned, and what comes next.
The bottom line
A mistrial is a trial that ends without verdict. The most common cause is a hung jury; other causes include juror misconduct, prosecutorial or defense errors, and manifest necessity. Retrial is generally permitted but is sometimes barred by double-jeopardy when intentional prosecutorial misconduct provoked the mistrial. The interim before the next trial allows both sides to reassess. A mistrial is neither inherently good nor bad — the strategic implications depend on what the trial looked like and what each side learned.
Frequently asked questions
Can the prosecution retry me after a mistrial in Missouri?
Usually yes. Mistrials are generally not double-jeopardy bars. The defendant can be retried after a hung-jury mistrial, after a mistrial declared with the defendant's consent, or after a mistrial based on manifest necessity. Retrial is barred only when the mistrial was caused by intentional prosecutorial misconduct designed to provoke it (Oregon v. Kennedy, 456 U.S. 667).
What is a hung jury?
A jury that cannot reach the unanimous verdict required for a Missouri criminal verdict. The judge polls the jurors, confirms they are deadlocked beyond reasonable hope of progress, and declares a mistrial. The prosecution may then retry, accept a plea, or dismiss.
Will I stay in jail during the time between a mistrial and retrial?
Generally bond status remains unchanged. Defendants on bond before trial typically remain on bond. Defendants who were in custody typically remain in custody — though sometimes mistrials provide an opportunity to revisit bond, particularly if the trial revealed weaknesses in the prosecution's case.
How long does it take to retry a Missouri criminal case after a mistrial?
Usually a few weeks to several months. The court resets the docket, both sides prepare for the second trial, and the trial is rescheduled. Some cases retry quickly because the witnesses and evidence are still fresh; others wait months or longer.
Does a mistrial mean I won my case?
No. A mistrial is not an acquittal. The case is not over — it just hasn't been decided. The state can usually retry. That said, hung-jury mistrials and prosecution-misconduct mistrials often improve the defendant's negotiating position substantially. Many cases that mistrial end up resolving favorably afterward through plea or dismissal.
Can I be tried multiple times for the same offense in Missouri?
Yes — within the constitutional limits. Mistrials don't trigger double-jeopardy in most cases. Hung juries can be tried again. Mistrials caused by manifest necessity allow retrial. The double-jeopardy clause bars only successive prosecutions after a verdict has actually been reached (acquittal or conviction) and certain narrow categories of mistrial.
This article is general legal information for Missouri residents. It is not legal advice. Missouri law changes regularly — statutes are amended, case law evolves, and the application of any rule depends on the specific facts of each case. Do not act, or refrain from acting, based on this article without consulting a qualified Missouri attorney about your particular situation. Reading this article does not create an attorney-client relationship. For advice on your specific case, contact David Naumann & Associates at (314) 831-9350. The initial consultation is free. See the full Legal Disclaimer for complete terms.