In a case drawing attention from states and groups nationwide, the U.S. Supreme Court will hear arguments in January on a constitutional challenge to Florida’s use of six-person juries in most felony criminal trials.

The federal government and 26 states, including Arizona, have backed Florida’s argument that it isn’t required to use 12-person juries in felony cases, while groups ranging from the NAACP and the U.S. Conference of Catholic Bishops to the Libertarian Cato Institute say the system should be struck down.

The Supreme Court last week scheduled oral arguments for Jan. 13 in an appeal filed by Hamed Kian, who was found guilty in 2023 by a six-person jury in Palm Beach County on charges of practicing chiropractic medicine with a suspended license. In June, the Supreme Court said it would take up the case.

Kian’s attorneys, including former U.S. Solicitor General Seth Waxman, contend that 12-member juries date back to the nation’s founding and that the Supreme Court incorrectly upheld Florida’s system in 1970 in Williams v. Florida. In an August brief, they wrote that allowing fewer than 12 jurors increases the odds that “the jury will not include a true cross-section of the community — and that the members who belong to a racial, religious, or cultural minority will be given fewer opportunities to express their views.”

“Numerous studies have established that a six-person jury is less representative, less consistent, and more likely to rule against a criminal defendant than a jury of 12,” Kian’s attorneys wrote.

But Florida Attorney General James Uthmeier’s office argued in a September brief that the U.S. Constitution’s Sixth Amendment, which includes a right to trial by a jury, “makes no mention” of 12 jurors. Florida requires 12-person juries in capital cases, such as first-degree murder trials, but otherwise uses six-member juries.

“In sum, history shows that 12-person juries were usual but not universal; opinions diverged on whether a 12-person jury was essential; jury size varied over the years, across locations, and in different circumstances; and the Framers left the specifics of jury composition to Congress and state legislatures,” the state’s brief said.

The Supreme Court’s decision in Kian could affect other states and federal courts. Arizona, Connecticut, Indiana, Louisiana, Massachusetts, and Utah allow juries of fewer than 12 people in at least certain felony cases, while federal courts can have 11-member juries if jurors are excused after deliberations have begun, according to briefs.

Attorneys general from Arizona, Connecticut, Indiana, Louisiana, and Utah wrote or signed briefs supporting Florida. Florida and other states argued that a ruling for Kian could force them to reopen cases where defendants are appealing convictions.

“These cases involve serious felonies, including homicides, sexual offenses, and violent crimes,” lawyers in Arizona Attorney General Kristin Mayes’ office wrote in one of the briefs. “Further, if Williams is not upheld, these states expect substantial post-conviction litigation, as well as significant additional expenditures such as rebuilding courtrooms to accommodate juries of 12 in jurisdictions that have traditionally used panels of six or eight. It will also pose greater challenges for rural communities that already face difficulties in seating sufficient jurors.”

Florida began using six-member juries in 1877, and the state’s modern-era Constitution effectively allows them, stating, “the number of jurors, not fewer than six, shall be fixed by law.”

Florida’s brief said the change was made in the 1870s after concerns that the “jury system was consuming one third” of the state budget. But NAACP attorneys argued in a Supreme Court brief that the state’s move to six-member juries as Reconstruction ended was designed to “thwart Black jury service.”

“By restricting access to jury service and reducing the size of juries, Florida made it easier to prosecute and convict Black people during the Jim Crow era and beyond,” the NAACP brief said.

Attorneys for Kian wrote in their August brief that the 1970 Williams ruling was “egregiously wrong.” Partially quoting another Supreme Court precedent, they said that “by any historical metric, the 12-person jury requirement falls within ‘what the term ‘trial by an impartial jury’ meant at the time of the Sixth Amendment’s adoption.’”

“The Williams decision has also had real-world negative consequences: It increases the odds of an erroneous conviction and decreases the representative nature of the juries in the affected States,” the brief said.

But lawyers in Uthmeier’s office wrote that the Williams ruling has “aged well.”

“The Sixth Amendment does not require that juries always consist of twelve members,” the state’s brief said. “Its text makes no mention of 12. And the historical evidence isn’t as simple as Petitioner suggests. Jury size has varied significantly over the centuries. Even when the default size was 12, legislatures always modified it. And the jury’s core purpose — interposing a body of laymen between the state and individual — doesn’t turn on a 12-juror composition.”