Hamed Kian was convicted in Florida state court by a criminal jury of only six members. The Supreme Court has recognized that the scope of the Sixth Amendment’s jury right should be determined based on the understanding of that right at the time the Amendment was ratified. But despite centuries of historical evidence establishing that juries must be composed of at least twelve members, the Supreme Court held in a 1970 case called Williams v. Florida that a jury with fewer than twelve members was compatible with the Sixth Amendment. In August 2026, the Constitutional Accountability Center filed an amicus brief explaining why the Supreme Court should overturn Williams and recognize that the twelve-person jury is a constitutional floor.

First, the Founding generation’s understanding of the jury right traces to English common law, which long recognized the jury as critical to preserving liberty. At common law, a jury was defined by the number of people who served on it: twelve. As Blackstone explained in his influential treatise, a person could not be “affected either in his property, his liberty, or his person, but by the unanimous consent of twelve of his neighbours and equals.” The Framers shared this belief that a “jury”—as that term was used in the Sixth Amendment’s jury-trial guarantee—required twelve people. During the debates on ratification and soon after, leading American thinkers assumed that the Constitution’s references to juries necessarily meant a group of twelve. Across the following centuries, the Supreme Court, state supreme courts, and influential legal thinkers continued to recognize that a jury must consist of twelve members.

Second, the Williams Court improperly dismissed the role of this established history in determining the meaning of the jury right. In the years since Williams, the Supreme Court has repeatedly made clear that the Sixth Amendment’s scope is defined by its original meaning, not a free-floating functional analysis.  In concluding that the Sixth Amendment did not embody the full common-law jury right, the Williams Court drew on deletions from Madison’s original draft of the Amendment, which removed specified attributes like a jury’s size and unanimity. But such deletions just as easily show that Madison’s specifications were considered unnecessary in light of the longstanding meaning of “jury” at the time of the Founding.

Finally, the Williams Court instead applied an ahistorical functional analysis to conclude that there were no “discernible difference” between twelve- and six-person juries.  But numerous empirical studies, including many conducted post-Williams, confirm that twelve-member juries perform markedly better along every measure Williams found critical. They provide for more considered deliberations; they more accurately discuss evidence and engage with probative information; they better represent a cross-section of the community; and they produce higher-quality verdicts, including by decreasing the odds that innocent defendants will be convicted. Williams thus erred in concluding that juries of six and of twelve were functional equivalents.