Motion for Mistrial: When Trials Go Wrong and How Lawyers Respond

A motion for mistrial asks the court to terminate an ongoing trial because a procedural error, prejudicial event, or jury issue has made a fair verdict impossible. A mistrial does not decide the case; it ends the present trial and typically allows the prosecution or plaintiff to retry, though double jeopardy or strategic considerations may bar retrial in some criminal cases. Mistrials are rare and usually granted only when no curative instruction will repair the prejudice.

The sections below address the standard for granting a mistrial, the most common grounds (inadmissible evidence, juror misconduct, hung juries), the procedural mechanics of making the motion, and the strategic implications for both sides. Read it beside the motion in limine guide for prevention strategy and the motion to vacate overview for post-trial relief.

Mistrial Standard

A mistrial is the trial-court remedy of last resort. The party requesting it must show that the prejudicial event is so serious that no curative jury instruction can salvage a fair verdict. Courts apply a strong presumption against mistrial because retrials waste judicial resources, burden witnesses, and disturb verdicts that may still have been just. The judge has substantial discretion, and a denial is reviewed for abuse of discretion on appeal.

Common Grounds for Mistrial

The frequent grounds for mistrial fall into three categories:

Federal practice on mistrial in civil cases draws from Federal Rule of Civil Procedure 59(a), which authorizes a new trial for any reason for which a new trial has heretofore been granted. In criminal cases the leading authority is Arizona v. Washington, 434 U.S. 497 (1978), establishing the manifest-necessity standard a judge must satisfy before declaring a sua sponte mistrial without barring retrial under the Double Jeopardy Clause. Federal Rule of Criminal Procedure 26.3 requires the court to consult the parties and consider alternatives before declaring a mistrial. The Sixth Circuit applied these principles in Renico v. Lett, 559 U.S. 766 (2010), holding that abuse-of-discretion review controls habeas review of state mistrial rulings.

Category	Examples	Likelihood of grant
Prejudicial evidence or argument	Inadmissible character evidence; references to settlement; mention of insurance; prior bad acts	Moderate; usually only after curative instruction fails
Juror misconduct	Outside research, premature deliberation, contact with parties, dishonesty in voir dire	Moderate; depends on the misconduct's likely effect
Hung jury	Jury cannot reach unanimous verdict after deliberation and Allen charge	Common; often the procedural endpoint
Court or counsel misconduct	Improper closing argument, judicial bias, prosecutor reference to defendant's silence	Moderate; varies by judge
Necessity	Death or illness of essential party, witness, or juror; physical disaster	High; manifest necessity

Hung Jury

The most common reason a judge declares a mistrial is a hung jury (a jury that cannot reach the unanimous verdict required in criminal cases or the threshold required in civil cases). After extended deliberation, the judge typically gives an Allen charge urging continued effort. If deadlock persists, the judge declares a mistrial and the case may be retried with a new jury. Hung juries occur in approximately 5 to 10 percent of jury trials.

Inadmissible Evidence

When a witness blurts out inadmissible evidence (a prior conviction, a settlement offer, an excluded photograph), the standard remedy is an instruction to disregard. A mistrial is appropriate only when the evidence is so prejudicial that the jury cannot reasonably be expected to ignore it. Courts often distinguish between inadvertent slips and deliberate elicitation; the latter is treated more harshly.

Juror Misconduct

Jurors who conduct outside research (looking up the defendant on social media, visiting the scene, consulting a dictionary), discuss the case before deliberation, or hide material information during voir dire create grounds for mistrial. The court typically conducts a hearing with the juror outside the others' presence, then evaluates whether the misconduct affected the verdict. A single juror can be replaced with an alternate; misconduct affecting multiple jurors is more likely to require mistrial.

Manifest Necessity in Criminal Cases

The Double Jeopardy Clause prevents retrial after acquittal and sometimes after a mistrial. To avoid the bar, the trial must end on grounds of "manifest necessity." Hung juries and physical impossibility (witness death, courthouse fire) clearly satisfy manifest necessity. Mistrials at the prosecution's request for tactical reasons or to gain advantage do not, and may bar retrial entirely. Defense-requested mistrials almost never bar retrial; the defendant has consented to ending the trial.

Procedural Mechanics

The motion is typically oral and made on the record at the moment the prejudicial event occurs. Waiting until after the verdict usually waives the issue. The party must:

1. Object contemporaneously when the prejudicial event happens.
2. Request a curative instruction if appropriate.
3. Move for mistrial when the curative instruction is inadequate.
4. Make a record sufficient for appellate review (request a sidebar transcript, file a written supplement after the day's proceedings).

If the court denies the motion, the issue is preserved for appeal. The losing party may renew the motion in a post-trial motion under Rule 59 if new information about the misconduct comes to light.

Effect on Retrial

If a mistrial is granted, the case is in the same procedural posture as before trial began. The prosecution or plaintiff may retry unless double jeopardy bars it (criminal cases without manifest necessity), the statute of limitations has run, or the parties settle. New evidence, new attorneys, and lessons learned from the first trial often shape the retrial significantly.

Whether retrial follows turns on Double Jeopardy analysis under the Fifth Amendment. If the defendant moved for the mistrial, retrial is presumptively allowed unless the prosecutor goaded the motion (see Oregon v. Kennedy, 456 U.S. 667 (1982)). If the court declared mistrial sua sponte, retrial requires manifest necessity under Arizona v. Washington. ABA Model Rule 3.4(c) and 3.4(e) bind the lawyer who provoked the mistrial: a lawyer shall not knowingly disobey an obligation under the rules of a tribunal or allude to matter the lawyer does not reasonably believe is relevant.

Strategic Considerations

A mistrial cuts both ways. The party that obtains a mistrial preserves the chance to retry but loses the time, effort, and money invested in the first trial. A criminal defendant who triggers a mistrial through misconduct can sometimes face retrial despite double jeopardy concerns. A civil defendant whose witness made the prejudicial statement may face a costlier retrial with a more cautious adversary. Defense attorneys often prefer to let the trial finish and challenge the verdict on appeal, where reversal at least keeps the existing trial record intact.

When You Need an Attorney

Mistrial motions require split-second judgment in the courtroom and detailed appellate-grade record-making. Legal Tank's attorney-drafted motion for mistrial service handles the written motion, supporting declaration, and renewed post-trial motion if needed. The motion for mistrial template is free for self-represented filers. For prevention, see the motion in limine guide.

Frequently Asked Questions

What does motion for mistrial mean?

A mistrial occurs when a jury is unable to reach a verdict and there must be a new trial with a new jury, or when there is a serious procedural error or misconduct that would result in an unfair trial and the judge adjourns the case without a decision on the merits and awards a new trial. A motion for mistrial is the formal request a party makes asking the court to declare the trial defective and terminate it. The motion is the trial-court remedy of last resort, granted only when no curative instruction can repair the prejudice.

What is the most common reason that a judge declares a mistrial?

The most common reason is a hung jury: a jury that cannot reach the unanimous verdict required in criminal cases or the threshold required in civil cases after extended deliberation, including an Allen charge urging continued effort. Hung juries occur in approximately 5 to 10 percent of jury trials. After a hung-jury mistrial, the case may be retried with a new jury subject to double jeopardy and statute-of-limitations constraints. Other common grounds are inadmissible evidence and serious juror misconduct.

Does a mistrial mean the defendant goes free?

No. A mistrial does not decide the case on the merits and does not equal an acquittal. The prosecution or plaintiff typically may retry the case unless double jeopardy bars it (criminal cases that ended without manifest necessity), the statute of limitations has run, or the parties settle. A defendant whose first trial ended in a hung jury can be retried because the jury never reached a verdict.

Can a defendant request a mistrial?

Yes. Either party can move for mistrial. Defense-requested mistrials typically do not bar retrial under double jeopardy because the defendant has consented to ending the trial. Prosecution-requested mistrials require manifest necessity to avoid double-jeopardy bar, except where the mistrial was caused by defense conduct intended to provoke it. The motion is typically made orally on the record at the moment the prejudicial event occurs, with contemporaneous objection a near-mandatory predicate.