The difference between a mistrial and an acquittal comes down to finality. An acquittal is a formal “not guilty” finding that ends the case for good; a mistrial stops the trial without any verdict, usually leaving prosecutors free to start over with a new jury. That gap matters because of double jeopardy: an acquittal permanently blocks a retrial on the same charges, while a mistrial generally does not.
What a Mistrial Is
A mistrial is not a verdict. It is a judge’s decision to halt a trial before the jury reaches a conclusion, wiping the slate clean as though the trial never happened. The judge does not rule on guilt or innocence. The proceeding is declared void, and the case returns to the status it held before the trial began.
The most common trigger is a hung jury. A criminal conviction for any serious offense requires a unanimous verdict in both federal and state courts, so when jurors remain deadlocked after extended deliberation, the trial has nowhere to go.1Constitution Annotated. Amdt6.4.4.3 Unanimity of the Jury A judge will usually push the jury to keep trying before pulling the plug, and will declare a mistrial only after concluding that more deliberation won’t break the impasse.
Judges can also declare mistrials for reasons unrelated to deadlock. Juror misconduct, such as researching the case online or discussing it with outsiders, can poison the proceeding. An attorney making prejudicial statements in front of the jury, the accidental introduction of evidence the jury should never have seen, or the sudden unavailability of a juror or lawyer due to illness can all force a judge’s hand. The common thread is that something has gone wrong enough to make a fair verdict unreliable.
The Manifest Necessity Standard
When a defendant objects to a mistrial, the judge cannot simply call it off. The Supreme Court established in 1824 that a mistrial declared over the defendant’s objection is only valid when there is “manifest necessity” for ending the trial, or when continuing would defeat the interests of justice.2Legal Information Institute. Reprosecution After Mistrial A deadlocked jury clearly meets that standard. So does discovering that a juror is disqualified, or that an error occurred so serious any resulting conviction would be reversed on appeal. When the problem stems from something the prosecution did, courts apply a harder look.
This matters because it controls whether the defendant can be retried. If a judge declares a mistrial without manifest necessity and over the defendant’s objection, double jeopardy may bar a second prosecution entirely.
What an Acquittal Is
An acquittal is a final determination that the defendant is not guilty. It does not necessarily mean the defendant is factually innocent. It means the prosecution failed to prove guilt beyond a reasonable doubt, the highest standard of proof in the legal system.3Legal Information Institute. Beyond a Reasonable Doubt Plenty of acquitted defendants probably did what they were accused of. The jury simply was not convinced enough to say so.
Most acquittals come from a jury that deliberates and unanimously votes “not guilty.” Once the foreperson announces that verdict, the case is over.
When the Judge Acquits
A defendant does not always need the jury’s help. Under Rule 29 of the Federal Rules of Criminal Procedure, a judge can enter a judgment of acquittal if the prosecution’s evidence is so weak that no reasonable jury could find the defendant guilty.4Legal Information Institute. Directed Verdict This typically happens after the prosecution rests but before the defense puts on witnesses. The case never reaches the jury at all.
Judges don’t use this power often. The bar is high: the evidence must be so insufficient that there is nothing for reasonable jurors to debate. When it happens, the acquittal carries the same finality as a jury verdict.
Acquittals on Some Counts, Not Others
When a defendant faces multiple charges, the jury can acquit on some counts while convicting or deadlocking on others. The acquitted charges are permanently resolved and can never be retried.5Constitution Annotated. Amdt5.3.6.2 Acquittal by Jury and Re-Prosecution If the jury deadlocks on the remaining counts, the judge declares a mistrial on those specific charges, and the prosecution can choose whether to retry only those unresolved counts.
Why the Distinction Matters: Double Jeopardy
The Fifth Amendment says no person shall “be subject for the same offence to be twice put in jeopardy of life or limb.”6Congress.gov. Amdt5.3.1 Overview of Double Jeopardy Clause That clause draws a bright line between the two outcomes.
When Jeopardy Attaches
Double jeopardy protection does not kick in when charges are filed. In a jury trial, jeopardy attaches when the jury is sworn in. In a bench trial, it attaches when the first witness begins testifying.7Legal Information Institute. Jeopardy Before those points, the prosecution can drop and refile charges without any double jeopardy issue.
Acquittal Blocks Retrial Completely
An acquittal triggers the strongest double jeopardy protection the law offers. Once a defendant is found not guilty, the government cannot appeal the verdict, retry the case, or bring the same charges again under any circumstances. It does not matter if damning new evidence surfaces the next day, if the jury clearly got it wrong, or if the judge misread the law when acquitting. The Supreme Court has described the ban on retrial after acquittal as “the most fundamental rule in the history of double jeopardy jurisprudence.”8Constitution Annotated. Amdt5.3.6.1 Overview of Re-Prosecution After Acquittal
The rationale is simple. Allowing the government to keep trying until it gets a conviction would let prosecutors wear down even innocent defendants through sheer resources and repetition.
Mistrial Usually Leaves Retrial on the Table
A mistrial generally does not trigger double jeopardy protection because no verdict was ever reached. Jeopardy attached when the jury was sworn in, but it did not terminate in the defendant’s favor. That distinction allows the prosecution to bring the defendant back for a new trial on the same charges.2Legal Information Institute. Reprosecution After Mistrial
There is one important exception. If the prosecution deliberately provoked the mistrial, intending to goad the defendant into asking for one, a retrial is barred. The Supreme Court set this standard in Oregon v. Kennedy, holding that a defendant who successfully moved for a mistrial can invoke double jeopardy only if the government’s misconduct was specifically designed to force that outcome.9Justia Law. Oregon v. Kennedy, 456 U.S. 667 (1982) The bar is intentionally high. Prosecutorial sloppiness or even recklessness is not enough; the defendant must show the misconduct was calculated to trigger a mistrial.
A Different Government Can Still Prosecute
Even an acquittal does not protect against prosecution by a different government. Under the dual-sovereignty doctrine, the federal government and each state government are separate sovereigns, so a crime that violates both federal and state law is technically two different offenses. The Supreme Court reaffirmed this in Gamble v. United States in 2019, holding that a state prosecution and a federal prosecution for the same conduct do not put a person in jeopardy twice for the “same offence.”10Justia Law. Gamble v. United States, 587 U.S. ___ (2019)
In practical terms, a defendant acquitted in state court could still face federal charges based on the same underlying conduct, and vice versa. The doctrine applies equally after mistrials, though the more common scenario there is simply a retrial by the same jurisdiction.
What Happens After Each Outcome
After an Acquittal
The consequences are immediate. If the defendant was in custody, they are released. Any bail money is returned, and all conditions of pretrial release, including check-ins, curfews, and travel restrictions, end. The criminal case is permanently closed, and the defendant walks away without a conviction.
What an acquittal does not do, and this catches many people off guard, is erase the arrest from the defendant’s record. In most states, the arrest and the charges still appear on a criminal background check even after a not-guilty verdict. The defendant typically must file a separate petition for expungement or record sealing to remove those entries. Eligibility rules and fees vary widely by state, but most jurisdictions do allow people to seal records from cases that ended in acquittal.
After a Mistrial
A mistrial leaves the defendant in limbo. The charges are still pending, and the prosecution must decide what comes next. Research on hung jury cases has found that roughly a third are retried before a new jury, about a third are resolved through plea agreements, and around a fifth are dismissed outright.
Several factors drive that decision. How close the jury was matters: an 11-1 split for conviction encourages prosecutors to retry, while a 6-6 deadlock sends a different signal about the strength of the case. Why the mistrial happened matters too. A mistrial caused by juror misconduct or a procedural error says nothing about the evidence, so prosecutors will almost certainly try again; a hung jury after a full trial suggests the evidence itself may be the problem. Witness availability can tip the balance, since a key witness who has moved or is no longer willing to testify may make retrial unrealistic. Cost also plays a role. Trials are expensive, and a second trial on a borderline case may not be the best use of a prosecutor’s budget or docket.
The prosecution may also use the mistrial as leverage to negotiate a plea deal, often offering reduced charges or a lighter sentence in exchange for avoiding another trial. For the defendant, accepting a plea after a mistrial is a difficult calculation. The first jury could not convict, but there is no guarantee the next one will deadlock again.
If the prosecution decides not to retry and dismisses the charges, the arrest and charges may still appear on the defendant’s record. As with acquittals, getting those entries removed usually requires a separate expungement petition.