Under the Constitution, the number of jurors required for a criminal case depends on which court is hearing it. Federal criminal trials use 12 jurors. State courts can use fewer, but never below six for a serious offense. And whatever the size, the jury’s decision to convict must be unanimous.
Federal Criminal Trials Use 12 Jurors
In federal court, the default is fixed. Federal Rule of Criminal Procedure 23 states that “A jury consists of 12 persons unless this rule provides otherwise.”1Cornell Law School. Federal Rules of Criminal Procedure Rule 23 The 12-person panel matches the English common law practice in place when the Bill of Rights was ratified, and federal courts have never moved off that number as the standard.
The rule leaves room for practical problems. If a juror has to be excused for good cause after deliberations start, the court can accept a verdict from the remaining 11 without needing both sides to consent. Judges in longer trials also seat alternates, up to six under Rule 24, who sit through the whole trial and can step in if a primary juror is dismissed.2Legal Information Institute. Federal Rules of Criminal Procedure Rule 24 – Trial Jurors When an alternate replaces a juror after deliberations have already begun, the jury has to start deliberating over.
State Courts Can Go as Low as Six
State practice looks different because the Sixth Amendment sets a floor, not a fixed number. The jury-trial right did not apply to states at all until Duncan v. Louisiana (1968), when the Supreme Court held that it was “fundamental to the American scheme of justice” and reached the states through the Fourteenth Amendment.3Justia Law. Duncan v. Louisiana, 391 US 145 (1968)
Two years later, in Williams v. Florida, the Court upheld Florida’s six-person criminal jury, concluding that the number 12 was a historical accident rather than a constitutional command. A six-member panel, the Court found, could serve the jury’s protective function just as well.4Oyez. Williams v. Florida
That prompted the follow-up question of how small was too small. The Court answered it in Ballew v. Georgia (1978), striking down a misdemeanor conviction returned by a five-person jury. Drawing on research about group deliberation, the Court held that juries below six cannot deliberate effectively or represent a cross-section of the community, and that five-person juries violate the Sixth and Fourteenth Amendments.5Cornell Law Institute. Amendment VI Rights in Criminal Prosecutions – Size of the Jury
So six is the constitutional minimum for a criminal jury in any court in the country.
How States Actually Structure Their Juries
Most states use 12-person juries for felonies, especially the most serious ones, but many allow smaller panels for lower-level charges. Arizona requires 12 jurors only when the possible sentence is death or 30 years or more in prison; other criminal cases in Arizona courts of record are tried before eight jurors. Other states use six-person juries for misdemeanors while keeping 12 for felonies.
Two people accused of similar conduct can therefore face very different jury sizes. A federal defendant will face 12. A state defendant might face 12, eight, or six, depending on the offense and the state’s rules.
Not Every Criminal Charge Triggers a Jury at All
Before jury size becomes relevant, the charge has to be serious enough to bring the jury-trial right into play. In Baldwin v. New York (1970), the Supreme Court held that any offense carrying a maximum sentence of more than six months in jail is a “serious” offense with a jury-trial right. If the maximum authorized sentence is six months or less, the offense is presumptively petty and the defendant is not entitled to a jury.6Legal Information Institute. Petty Offense Doctrine and Maximum Sentences Over Six Months
Blanton v. City of North Las Vegas (1989) added that a defendant charged with a presumptively petty offense can still obtain a jury trial by showing that additional penalties beyond the short jail term are severe enough that the legislature must have treated the crime as serious. In practice, that is a hard showing to make.7Justia Law. Blanton v. City of No. Las Vegas, 489 US 538 (1989)
Stacking petty charges does not help either. In Lewis v. United States, the Court held that when several petty offenses are tried together and the combined potential sentence exceeds six months, the jury-trial right still turns on the maximum for each individual count, not the total.6Legal Information Institute. Petty Offense Doctrine and Maximum Sentences Over Six Months
The Verdict Must Be Unanimous
Size is only half of the constitutional picture. To convict, every seated juror must agree.
For decades, Louisiana and Oregon allowed criminal convictions based on 10-to-2 votes. That practice ended in 2020 with Ramos v. Louisiana. Evangelisto Ramos had been convicted of second-degree murder and sentenced to life without parole on a 10-to-2 verdict. The Supreme Court held that the Sixth Amendment requires a unanimous verdict to convict a defendant of a serious offense, and that the requirement applies equally in state and federal courts.8Supreme Court of the United States. Ramos v. Louisiana (18-5924) The Court grounded its ruling in the common-law record: unanimity was a settled feature of jury trials when the Sixth Amendment was adopted.9Oyez. Ramos v. Louisiana
The interaction between size and unanimity had already been addressed for the smallest juries. In Burch v. Louisiana (1979), the Court held that non-unanimous verdicts by six-person juries are unconstitutional, reasoning that shrinking a jury to the constitutional minimum while also allowing split verdicts undermines the protections the size floor was meant to preserve.10Cornell Law Institute. Burch v. Louisiana, 441 US 130 (1979) After Ramos, the same rule applies at every jury size: one juror voting to acquit is enough to prevent a conviction.
Ramos Does Not Reopen Older Convictions
Defendants convicted by non-unanimous juries before Ramos cannot use the decision to undo those convictions on federal habeas review. In Edwards v. Vannoy (2021), the Supreme Court held that the Ramos rule is a new rule of criminal procedure that does not apply retroactively to cases already final on direct appeal. The Court also said the “watershed” exception that might have allowed retroactive relief is effectively closed off going forward.11Supreme Court of the United States. Edwards v. Vannoy (19-5807) People whose non-unanimous convictions became final before April 2020 have to look to state-law remedies, which vary.
When Jurors Cannot Agree
Because unanimity is required, hung juries happen. When jurors tell the judge they cannot reach a verdict, the judge typically has two moves before declaring a mistrial. The first is an Allen charge, a supplemental instruction telling jurors to keep deliberating, to reconsider their positions, and to change their minds if genuinely persuaded, while not abandoning an honest belief just to produce a verdict.
If deliberations still fail, the judge declares a mistrial. A mistrial from a hung jury does not bar retrial. Jury deadlock is a classic example of the “manifest necessity” that permits a second prosecution without violating the Double Jeopardy Clause.12Legal Information Institute. Reprosecution After Mistrial The prosecution can retry the case, offer a plea, or drop the charges. There is no constitutional cap on the number of retries after successive hung juries, though prosecutors rarely take a case through more than one or two.