Hung Jury and Mistrial Explained

A hung jury and a mistrial are two distinct but closely related procedural outcomes that can halt a trial before a final verdict is reached. This page covers their definitions, the legal mechanisms that trigger them, the circumstances that produce them most often, and the boundaries courts use to distinguish one outcome from another. Understanding these concepts is essential for interpreting how the American trial system handles unresolved or compromised proceedings.

Definition and scope

A mistrial is a formal judicial declaration that terminates a trial before its natural conclusion — typically before a verdict — because of a defect so fundamental that continuing the proceeding would be unjust or legally invalid. A hung jury is one specific cause of a mistrial: it occurs when the jury cannot reach the unanimous verdict required under the applicable legal standard after extended deliberation.

The two terms are frequently used interchangeably in informal usage, but they occupy different positions in procedural law. A mistrial is the judicial act; a hung jury is one factual predicate that may compel that act. Other causes of mistrial include juror misconduct, improper contact with jurors, prejudicial publicity, a deadlocked jury, death or serious illness of a juror during trial, or fundamental errors in the proceedings — such as inadmissible evidence placed before the jury in violation of the rules of evidence.

The governing framework for mistrials in federal courts derives from the Federal Rules of Criminal Procedure (Fed. R. Crim. P.), with Rule 26.3 specifically requiring that the court provide an opportunity for the parties to be heard before declaring a mistrial (Federal Rules of Criminal Procedure, Rule 26.3). State courts follow analogous rules under their own procedural codes.

The scope of this topic spans both criminal trial proceedings and civil trial proceedings, though the unanimity requirement that most often produces a hung jury applies primarily in criminal cases.

How it works

When jurors retire to deliberate, they operate under instructions provided by the judge — typically including a requirement that the verdict be unanimous in criminal proceedings, as established by the Sixth Amendment as interpreted in Ramos v. Louisiana, 590 U.S. 83 (2020), which held that the Sixth Amendment's unanimity requirement applies to state felony trials (Ramos v. Louisiana, 590 U.S. 83 (2020)). The process by which a hung jury is declared follows a structured sequence:

Initial deadlock reported — The jury foreperson notifies the judge in writing or verbally that deliberations have stalled and no consensus appears reachable.
Allen charge considered — The judge may issue an "Allen charge" (also called a dynamite charge), a supplemental instruction urging jurors to reconsider their positions while not abandoning sincerely held views. The Allen charge originates from Allen v. United States, 164 U.S. 492 (1896) (Allen v. United States, 164 U.S. 492 (1896)).
Continued deadlock confirmed — If deliberations still yield no verdict after the Allen charge, the judge polls the jury or receives a second report of irreconcilable disagreement.
Mistrial declared — The presiding judge formally declares a mistrial on the record, specifying the basis (e.g., hung jury).
Post-mistrial posture determined — The prosecution or plaintiff decides whether to retry the case, negotiate a resolution, or dismiss charges.

In civil cases under Federal Rule of Civil Procedure 48, the required number of jurors who must agree is set at a minimum of 6 out of a seated panel of 6–12, and parties may stipulate to a non-unanimous verdict (Fed. R. Civ. P. 48).

Common scenarios

Hung juries arise most frequently in fact-intensive cases where witness credibility is contested, where the evidence is circumstantial, or where jurors hold fundamentally divergent interpretations of the burden of proof. The following scenarios represent the most documented patterns:

High-profile criminal prosecutions — Cases attracting intense public attention often seat juries with members holding entrenched pre-existing views, increasing the probability of irreconcilable disagreement.
Complex financial or white-collar cases — Juries confronting voluminous documentary evidence and technical expert testimony sometimes fragment along comprehension lines rather than factual assessment. The use of expert witnesses can cut in either direction.
Cases with deeply contested eyewitness accounts — When the primary evidence is conflicting testimony rather than physical evidence, individual juror credibility assessments diverge.
Emotionally charged cases — Charges involving allegations of violence, sexual misconduct, or domestic harm frequently produce a subset of jurors who are influenced by factors outside the evidentiary record, making unanimity harder to achieve.
Non-deadlock mistrials — A juror discovered to have lied during jury selection, a juror who independently researches the case, or a juror who communicates with a party can trigger a mistrial without any deliberation occurring.

Research published by the National Center for State Courts has documented hung jury rates in felony trials at approximately 6 percent nationally, with rates exceeding 15 percent in jurisdictions such as Los Angeles County for certain case categories (National Center for State Courts, "Are Hung Juries a Problem?" 2002).

Decision boundaries

The most significant legal boundary associated with a mistrial is its interaction with the Double Jeopardy Clause of the Fifth Amendment. Under the Double Jeopardy Clause, a defendant cannot be tried twice for the same offense after an acquittal or conviction. A mistrial, however, does not automatically bar retrial — the constitutional analysis turns on whether the mistrial was declared with manifest necessity or with the defendant's consent.

The manifest necessity doctrine, articulated in United States v. Perez, 22 U.S. 579 (1824) (United States v. Perez, 22 U.S. 579 (1824)), permits retrial when a hung jury arises from genuine deadlock. By contrast, if a prosecutor or judge engineers a mistrial to escape an unfavorable evidentiary posture, double jeopardy protection may bar retrial.

Key classification contrasts:

Dimension	Hung Jury Mistrial	Prosecutorial/Judicial Misconduct Mistrial
Retrial permitted?	Yes — manifest necessity established	No — if declared without defendant's consent to escape adverse outcome
Jeopardy attachment	Attaches at jury empanelment (criminal)	Same attachment point
Governing doctrine	Perez manifest necessity	Oregon v. Kennedy, 456 U.S. 667 (1982) (link)
Double Jeopardy bar	Does not apply	Applies when prosecution deliberately provokes mistrial

The distinction between a valid hung jury mistrial and a mistrial caused by judicial or prosecutorial error is therefore not academic — it determines whether the defendant faces a second trial. Courts examine the trial record, the timing of the mistrial motion, and whether the moving party had a tactical interest in terminating the proceeding before verdict. This analysis intersects with protections addressed under fifth amendment rights at trial and outcomes catalogued under trial verdict types and meanings.

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