Amicus Curiae Brief — Hamed Kian, Petitioner v. Florida

No. 25-6623

IN THE

Supreme Court of the United States

HAMED KIAN,

Petitioner,

v.

STATE OF FLORIDA,

Respondent.

On Writ of Certiorari to the

Florida Fourth District Court of Appeal

BRIEF OF THE NATIONAL ASSOCIATION OF

CRIMINAL DEFENSE LAWYERS AS AMICUS

CURIAE IN SUPPORT OF PETITIONER

Jonathan D. Hacker

Co-Chair, Supreme Court

Amicus Committee

NATIONAL ASSOCIATION OF

CRIMINAL DEFENSE LAWYERS

1660 L St., NW

Washington, DC 20036

Arjun Ogale

GIBSON, DUNN & CRUTCHER LLP

2001 Ross Ave., Ste. 2100

Dallas, TX 75201

Matt Aidan Getz

Counsel of Record

Kahn A. Scolnick

Patrick J. Fuster

Paige H. Petrashko

GIBSON, DUNN & CRUTCHER LLP

333 South Grand Ave.

Los Angeles, CA 90071

(213) 229-7754

mgetz@gibsondunn.com

Tate Rosenblatt

GIBSON, DUNN & CRUTCHER LLP

1700 M St. N.W.

Washington, DC 20036

Counsel for Amicus Curiae

i

TABLE OF CONTENTS

Page

INTEREST OF AMICUS CURIAE ........................... 1

SUMMARY OF ARGUMENT ..................................... 2

ARGUMENT ............................................................... 3

I.

The right to trial by jury always meant a right

to a jury of twelve .................................................3

II. Williams is grievously wrong and inflicting

grave harms ..........................................................7

A. Williams hastily balanced away a key

constitutional guarantee ................................7

B. A jury of twelve better serves the purposes

of the jury-trial right ......................................9

III. Overruling Williams would not have undue

consequences .......................................................16

CONCLUSION .......................................................... 19

ii

TABLE OF AUTHORITIES

Page(s)

Cases

Baldwin v. New York,

399 U.S. 66 (1970) ................................................ 18

Ballew v. Georgia,

435 U.S. 223 (1978) ............................................ 8, 9

Blakely v. Washington,

542 U.S. 296 (2004) .............................................. 10

Cancemi v. People,

18 N.Y. 128 (1858).................................................. 6

Cap. Traction Co. v. Hof,

174 U.S. 1 (1899) .................................................... 6

Carpenter v. State,

5 Miss. (4 Howard) 163

(High Ct. Err. & App. 1839) .................................. 6

Cunningham v. Florida,

144 S. Ct. 1287 (2024) ............................................ 8

Danforth v. Minnesota,

552 U.S. 264 (2008) .............................................. 18

Duncan v. Louisiana,

391 U.S. 145 (1968) .................... 3, 7, 10, 14, 15, 17

Edwards v. Vannoy,

593 U.S. 255 (2021) .............................................. 18

Emerick v. Harris,

1 Binn. 416 (Pa. 1808)............................................ 6

iii

Foote v. Lawrence,

1 Stew. 483 (Ala. 1828) .......................................... 6

Ex parte Grossman,

267 U.S. 87 (1925) .................................................. 4

Herrera v. Wyoming,

587 U.S. 329 (2019) .............................................. 16

Kahler v. Kansas,

589 U.S. 271 (2020) ................................................ 4

Khorrami v. Arizona,

143 S. Ct. 22 (2022) ........................................ 13, 16

Maxwell v. Dow,

176 U.S. 581 (1900) ................................................ 6

Patton v. United States,

281 U.S. 276 (1930) ...................................... 2, 7, 17

Powers v. Ohio,

499 U.S. 400 (1991) .............................................. 15

Ramos v. Louisiana,

590 U.S. 83 (2020) ............................... 3, 4, 8, 9, 13,

............................................................ 16, 17, 18, 19

Rassmussen v. United States,

197 U.S. 516 (1905) ................................................ 6

Taylor v. Louisiana,

419 U.S. 522 (1975) .............................................. 15

Teague v. Lane,

489 U.S. 288 (1989) .............................................. 18

Thompson v. Utah,

170 U.S. 343 (1898) ............................................ 5, 6

iv

United States v. Booker,

543 U.S. 220 (2005) .............................................. 18

Wesberry v. Sanders,

376 U.S. 1 (1964) .................................................... 6

Wheaton v. Peters,

33 U.S. (8 Pet.) 591 (1834) ................................. 2, 8

Whitehurst v. Davis,

3 N.C. (2 Hayw.) 113 (1800)................................... 6

Williams v. Florida,

399 U.S. 78 (1970) ........................... 2, 3, 7, 8, 9, 10,

................................................ 11, 13, 14, 15, 16, 18

Work v. State,

2 Ohio St. 296 (1853) ............................................. 6

Zylstra v. Corp. of Charleston,

1 S.C.L. (1 Bay) 382

(Ct. Com. Pl. 1794) ................................................. 5

Constitutional Provisions

U.S. Const. art. III, § 2 ................................................ 4

U.S. Const. amend. VI ..................... 4, 6, 16, 17, 18, 19

U.S. Const. amend. XIV ........................................ 7, 17

Statutes

Fla. Stat. § 913.10 ..................................................... 17

Rules

Fed. R. Crim. P. 23 .................................................... 17

Fed. R. Crim. P. 24 .................................................... 17

v

Historical Materials

Bacon, A New Abridgment of the Law

(4th ed. 1778).......................................................... 5

Bishop, Commentaries on the Law of

Criminal Procedure (1866) .................................... 6

Blackstone, Commentaries on the Laws

of England (1768) ............................................... 2, 5

Cooley, Constitutional Limitations

(1868) ...................................................................... 6

N.Y. Charter of Liberties & Privileges

(1683), in Lincoln, Constitutional

History of New York (1906) ................................... 5

Story, Commentaries on the Constitution

of the United States (1833) .................................... 9

Wilson, Of Juries,

in Collected Works of James Wilson

(Hall & Hall eds. 2007) .......................................... 6

Other Authorities

Amar, Reinventing Juries:

Ten Suggested Reforms,

28 U.C. Davis L. Rev. 1169 (1995) ...................... 13

Anwar et al., The Impact of Jury Race

in Criminal Trials,

127 Q. J. Econ. 1017 (2012) ........................... 14, 15

Arnold, Trial by Jury: The

Constitutional Right to a Jury of

Twelve in Civil Trials,

22 Hofstra L. Rev. 1 (1993) ............................ 12, 14

vi

Barkow, Recharging the Jury: The

Criminal Jury’s Constitutional Role

in an Era of Mandatory Sentencing,

152 U. Pa. L. Rev. 33 (2003) ................................ 10

Bates, Trial by Jury After

Williams v. Florida,

10 Hamline L. Rev. 53 (1987) ................................ 5

Carrington, The Seventh Amendment:

Some Bicentennial Reflections,

1990 U. Chi. Legal F. 33 .......................... 11, 12, 14

Kaye, And Then There Were Twelve:

Statistical Reasoning, the Supreme

Court, and the Size of the Jury,

68 Calif. L. Rev. 1004 (1980) ......................... 11, 12

Miller, Six of One Is Not a Dozen

of the Other: A Reexamination

of Williams v. Florida and the

Size of State Criminal Juries,

146 U. Pa. L. Rev. 621 (1998) ..................... 4, 8, 11,

.................................................................. 12, 14, 15

Roper, Jury Size and Verdict

Consistency: “A Line Has to Be

Drawn Somewhere”?,

14 L. & Soc'y Rev. 977 (1980) .............................. 11

Rossner & Tait, Virtual Technology and the

Changing Rituals of Courtroom Justice,

98 Chi.-Kent L. Rev. 251 (2023) .......................... 18

Saks & Marti, A Meta-Analysis of the

Effects of Jury Size,

21 Law & Hum. Behav. 451 (1997) ......... 11, 12, 14

vii

Sommers & Ellsworth, How Much Do We

Really Know About Race and Juries?:

A Review of Social Science Theory

and Research,

78 Chi.-Kent L. Rev. 997 (2003) .......................... 15

Su & Goravara, What Is a Jury?,

103 N.C. L. Rev. 969 (2025) ............................. 5, 12

Valenti & Downing, Six Versus Twelve

Member Juries: An Experimental Test

of the Supreme Court Assumption of

Functional Equivalence, 1 Personality

& Soc. Psychol. Bull. 273 (1974) .......................... 11

Zeisel, ... And Then There Were None:

The Diminution of the Federal Jury,

38 U. Chi. L. Rev. 710 (1971)..................... 8, 10, 13

IN THE

Supreme Court of the United States

No. 25-6623

HAMED KIAN,

Petitioner,

v.

STATE OF FLORIDA,

Respondent.

On Writ of Certiorari to the

Florida Fourth District Court of Appeal

BRIEF OF THE NATIONAL ASSOCIATION OF

CRIMINAL DEFENSE LAWYERS AS AMICUS

CURIAE IN SUPPORT OF PETITIONER

INTEREST OF AMICUS CURIAE*

The National Association of Criminal Defense

Lawyers, or NACDL, is a nonprofit voluntary professional bar association that works on behalf of criminal defense attorneys to ensure justice and due process for those accused of crimes or misconduct.

NACDL was founded in 1958 and has a nationwide

membership of many thousands of direct members

* No counsel for a party authored this brief in whole or in part,

and no entity or person other than NACDL, its members, and its

counsel made a monetary contribution intended to fund the preparation or submission of this brief.

2

and up to 40,000 attorneys in affiliate organizations.

NACDL is dedicated to advancing the proper, efficient, and fair administration of justice. NACDL

files many amicus briefs each year in this Court and

other federal and state courts, seeking to assist in

cases presenting issues important to criminal defendants, criminal defense lawyers, and the criminal

legal system as a whole.

SUMMARY OF ARGUMENT

I. Few rights were as cherished or as well settled

at the time of the Founding as the right to a trial by

jury in criminal cases. And when that right was twice

written into the Constitution, it carried established

characteristics—including that conviction required

“the unanimous consent of twelve.” 3 Blackstone,

Commentaries on the Laws of England 379 (1768).

The rule that trial by jury meant trial by twelve was

so firmly cemented at common law and so consistently

recognized by sources before, at, and following the

Founding that this Court once called the constitutional requirement of a twelve-person jury in criminal

cases “not open to question.” Patton v. United States,

281 U.S. 276, 288 (1930).

II. Only in Williams v. Florida, 399 U.S. 78 (1970),

did this Court depart from the path. There, the Court

recognized the historical, common-law, and constitutional heritage of twelve-member juries. But the

Court discarded that evidence on the basis that, in its

judgment, a jury of twelve was no longer worth requiring as a practical matter. That was a grave mistake.

For one thing, a rich common-law tradition warrants

respect because it reflects “the wisdom, counsel, experience and observation of many ages.” Wheaton v. Peters, 33 U.S. (8 Pet.) 591, 672 (1834). For another,

each of the vital interests served by the jury-trial right

3

is undermined by permitting criminal trials with sixor eight- rather than twelve-member juries. Juries of

twelve counteract prosecutorial and judicial overreach, produce accurate and sensible decisions, and

facilitate broad community participation in the criminal system. Reducing the number of jurors leads to

unjust convictions, overzealous prosecutions, and serious deficiencies in juror deliberations and reasoning.

III. Overruling Williams to restore the centuriesold requirement of a twelve-member jury would not

have undue consequences. The vast majority of the

States already comply with the Constitution’s original

meaning. The federal system does, too, permitting departures from twelve-member juries only in extraordinary circumstances that are not presented here.

Plus, any decision restoring the jury-trial right as the

Framers intended it would not yield any path to collateral attacks in cases involving final convictions.

Ultimately, any disruption involved in correcting

course and sweeping Williams into the dustbin of history “cannot outweigh the interest we all share in the

preservation of our constitutionally promised liberties.” Ramos v. Louisiana, 590 U.S. 83, 110-11 (2020)

(opinion of Gorsuch, J.). This Court should overrule

Williams and reverse the judgment below.

ARGUMENT

I.

The right to trial by jury always meant a

right to a jury of twelve.

Jury trials weren’t a new idea in 1791. When the

“Constitution was written, jury trial in criminal cases

had been in existence in England for several centuries

and carried impressive credentials traced by many to

Magna Carta.” Duncan v. Louisiana, 391 U.S. 145,

151 (1968). The Framers valued that right so much

4

that they enshrined it in the Constitution twice over.

U.S. Const. art. III, § 2 (“Trial of all Crimes . . . shall

be by Jury”); id. amend. VI (criminal defendants shall

have the right to trial “by an impartial jury” in “all

criminal prosecutions”). When the Framers twice insisted on trial by jury in criminal cases, they were

drawing from centuries of inherited “meaning about

the content and requirements of a jury trial.” Ramos v.

Louisiana, 590 U.S. 83, 89 (2020); accord, e.g., Ex parte

Grossman, 267 U.S. 87, 108-09 (1925) (the “language

of the Constitution cannot be interpreted safely except

by reference to the common law and to British institutions as they were when the instrument was framed

and adopted”).

Those centuries of practice taught a simple lesson:

a trial by “jury” meant trial by twelve, not six or eight.

That uninterrupted rule spanned 600 years, from its

common-law origins to early American practice

through this Court’s precedents up until 1970. See

Pet. Br. 18-23.

Start with the common law. The “twelve-person

unanimous criminal jury was an institution with a

nearly four-hundred-year-old tradition in England”

before the Sixth Amendment’s ratification. Miller, Six

of One Is Not a Dozen of the Other: A Reexamination

of Williams v. Florida and the Size of State Criminal

Juries, 146 U. Pa. L. Rev. 621, 643 (1998). Leading

English authorities equated the jury-trial right with a

right to trial by twelve jurors. See Kahler v. Kansas,

589 U.S. 271, 279 (2020) (in assessing “‘historical

practice,’” this Court “look[s] primarily to eminent

common-law authorities (Blackstone, Coke, Hale, and

the like)”). Blackstone, for instance, explained that a

person couldn’t be “affected either in his property, his

liberty, or his person, but by the unanimous consent

5

of twelve of his neighbours and equals.” 3 Blackstone,

Commentaries on the Laws of England 379 (1768).

Another influential treatise observed that a jury consists of “twelve, and can be neither more nor less.”

3 Bacon, A New Abridgment of the Law 234 (4th ed.

1778); see Thompson v. Utah, 170 U.S. 343, 350 (1898)

(citing Bacon’s Abridgment to underscore that trial by

jury was one of “the principal excellencies of our constitution” and required a “verdict of twelve”).

The colonists brought that common-law tradition

with them when they crossed the Atlantic. Several of

the colonies’ foundational documents used “twelve

men” as a proxy for the word “jury.” In its first legislative session, the New York General Assembly provided that “Tryalls shall be by the verdict of twelve

men.” N.Y. Charter of Liberties & Privileges § 17

(1683), in 1 Lincoln, The Constitutional History of

New York 101 (1906). The Pennsylvania Frame of

Government likewise stated that “‘[a]ll trials shall be

by twelve men.’” See Su & Goravara, What Is a Jury?,

103 N.C. L. Rev. 969, 998 (2025). And early settlements in Virginia and New Plymouth had scarcely

gained a foothold in the territory before the settlers

began insisting on twelve-person juries in criminal

cases. Bates, Trial by Jury After Williams v. Florida,

10 Hamline L. Rev. 53, 65 (1987).

Even where state constitutions didn’t specify that

the right to trial by “jury” meant a trial by twelve, no

one was confused about what “jury” meant. A South

Carolina court, for example, understood “jury” to

mean “12 men . . . indiscriminately drawn from every

class of their fellow citizens.” Zylstra v. Corp. of

Charleston, 1 S.C.L. (1 Bay) 382, 389 (Ct. Com. Pl.

1794). The Supreme Court of Pennsylvania similarly

explained that the unadorned term “trial by jury” in

6

its 1776 constitution preserved the requirement “‘that

all trials shall be by twelve men.’” Emerick v. Harris,

1 Binn. 416, 426 (Pa. 1808). And state high courts in

later decades continued the tradition of reading “jury”

in criminal cases to mean twelve people. See, e.g.,

Cancemi v. People, 18 N.Y. 128, 138 (1858); Work v.

State, 2 Ohio St. 296, 304 (1853); Carpenter v. State, 5

Miss. (4 Howard) 163, 166-67 (High Ct. Err. & App.

1839); Foote v. Lawrence, 1 Stew. 483, 483 (Ala. 1828);

Whitehurst v. Davis, 3 N.C. (2 Hayw.) 113, 113 (1800)

(per curiam).

Prominent legal thinkers at the Founding and in

later decades were on the same page. In lectures delivered in Philadelphia “drawing on his experience as

one of the most active members of the Constitutional

Convention,” Wesberry v. Sanders, 376 U.S. 1, 17

(1964), Justice Wilson expressed the view that “[t]o

the conviction of a crime, the undoubting and the

unanimous sentiment of the twelve jurors is of indispensable necessity.” Wilson, Of Juries, in 2 Collected

Works of James Wilson 985 (Hall & Hall eds. 2007).

Later treatises echoed the same view that “[a] jury of

less than twelve men is not a jury” at all, so “a statute

authorizing a jury of less, in a case in which the constitution guarantees a jury trial, is void.” 1 Bishop,

Commentaries on the Law of Criminal Procedure

§ 761, at 532 (1866); accord, e.g., Cooley, Constitutional Limitations 319 (1868).

Before 1970, this Court too consistently recognized

that the “jury referred to in the original constitution

and in the sixth amendment is a jury constituted, as it

was at common law, of twelve persons, neither more

nor less.” Thompson, 170 U.S. at 349; accord Cap.

Traction Co. v. Hof, 174 U.S. 1, 13 (1899); Maxwell v.

Dow, 176 U.S. 581, 586 (1900); Rassmussen v. United

7

States, 197 U.S. 516, 529 (1905); Patton v. United

States, 281 U.S. 276, 288 (1930). This right is so “fundamental to the American scheme of justice” that it is

incorporated against the States by the Fourteenth

Amendment. Duncan, 391 U.S. at 149, 158 n.30 (disregarding concerns about the practicability of enforcing the requirement of a twelve-member jury).

This Court had it right long ago: given the overwhelming historical record of what a “jury” in criminal

cases meant, the constitutional requirement of a

twelve-person jury “is not open to question.” Patton,

281 U.S. at 288.

II. Williams is grievously wrong and inflicting

grave harms.

Then came Williams v. Florida, 399 U.S. 78 (1970),

in which this Court took an unwarranted detour from

the common-law and constitutional tradition—and in

the process seriously undermined the jury-trial right.

Williams dismissed the requirement of a twelve-person

jury based on a smattering of since-debunked socialscience studies and its own views about the importance of jury size. That analysis was erroneous at

the time the Court decided Williams, and its harmful

ramifications are even more apparent in hindsight.

A. Williams hastily balanced away a key

constitutional guarantee.

Williams got off on the wrong foot by overlooking

the time-tested wisdom of the common law. This

Court did not deny the extensive history underlying

the twelve-member jury. Williams, 399 U.S. at 93-96.

But in the Court’s view, that historical tradition

amounted to little more than “mystical or superstitious insights” supporting an “accidental feature” of

the jury trial. Id. at 88, 90.

8

Instead of respecting the lessons and experiences

that informed the dedication to a twelve-person jury,

the Court in Williams attempted to weigh for itself

whether the jury’s size was “important enough” to preserve. Ramos, 590 U.S. at 98. In doing so, the Court

relied on a handful of dubious “experiments” to conclude that “the particular number of the body that

makes up the jury” was not an “essential feature” of

the right. Williams, 399 U.S. at 100-01. That was a

grave mistake.

Williams eschewed the wisdom inherent in “centuries of historical practice” in favor of “bad social science.” Cunningham v. Florida, 144 S. Ct. 1287, 128788 (2024) (Gorsuch, J., dissenting from denial of certiorari). Scholars debunked the studies on which Williams rested almost immediately. See, e.g., Zeisel,

. . . And Then There Were None: The Diminution of the

Federal Jury, 38 U. Chi. L. Rev. 710, 713-15 (1971)

(noting the “scant evidence” underpinning Williams);

Miller, supra, at 651 n.163 (collecting contemporaneous studies). And just a few years later, the Court itself acknowledged research “rais[ing] doubts about

the accuracy of the results achieved” by smaller juries,

which are “less likely to foster effective group deliberation.” Ballew v. Georgia, 435 U.S. 223, 232-38 (1978)

(plurality opinion).

By dismissing the past commitment to a twelvemember jury as arbitrary, Williams improvidently

cast off “everything history might have taught us

about what it means to have a jury trial.” Ramos, 590

U.S. at 98 (emphasis omitted). The common-law tradition “is not the product of the wisdom of some one

man, or society of men, in any one age, but of the wisdom, counsel, experience and observation of many

ages of wise and observing men.” Wheaton v. Peters,

9

33 U.S. (8 Pet.) 591, 671-72 (1834). And long-held traditions “may serve purposes evading our current notice.” Ramos, 590 U.S. at 100.

Williams was wrong to discard those traditions

out of hand. This Court should correct course, restore

the historical and common-law right on which the

Framers insisted, and overrule Williams.

B. A jury of twelve better serves the purposes of the jury-trial right.

Williams also should be overruled because its

rushed analysis of the purposes and effects of the

twelve-member jury requirement has not withstood

the test of time. This Court has identified three primary goals that the jury-trial right serves: (1) “the interposition between the accused and his accuser of the

commonsense judgment of a group of laymen,” Williams, 399 U.S. at 100; (2) “promot[ing] group deliberation,” Ballew, 435 U.S. at 230 (plurality opinion); and

(3) “provid[ing] a representative cross-section of the

community,” ibid. Social science and experience alike

reveal that a jury of twelve better serves each of these

goals as compared to six- or eight-member juries of the

kind seen in select States. See Pet. Br. 30-34. Ultimately, then, restoring the twelve-person jury guaranteed at common law will not only bring the Constitution back in line with original public meaning, but

also ensure that the various benefits of the twelve-person jury are felt across the criminal system—and by

the public more generally.

1. Juries are an essential democratic check

against prosecutorial and judicial overreach. 3 Story,

Commentaries on the Constitution of the United

States § 1774, at 653 (1833). Because juries are outside the government, they “function as [the]

10

circuitbreaker in the [government’s] machinery of justice.” Blakely v. Washington, 542 U.S. 296, 306 (2004).

The government and the judge are both “repeat

player[s] in the criminal justice process,” and as a result they can “become desensitized to the enormity of

what is at stake in a criminal proceeding.” Barkow,

Recharging the Jury: The Criminal Jury’s Constitutional Role in an Era of Mandatory Sentencing, 152 U.

Pa. L. Rev. 33, 72 (2003).

Requiring trial by jury ensures that criminal

cases are seen “with a fresh set of eyes” and with “no

institutional bias.” Barkow, supra, at 72. Juries impose their own sense of fair play and are not desensitized to the stakes of one prosecution for having seen

so many other prosecutions. In short, wherever a defendant “preferred the common-sense judgment of a

jury,” he “was to have it.” Duncan, 391 U.S. at 156.

It is easy to see why a jury of fewer than twelve

provides less of a bulwark. “To obtain a conviction under the unanimity rule, the prosecutor must persuade

the juror with the highest standard” of reasonable

doubt. Zeisel, supra, at 721. The prosecutor’s job becomes easier with every person plucked from the common-law rule of twelve because she can more likely

avoid “the class of jurors who are most difficult to convince.” Ibid. With only six or eight jurors, it becomes

far less likely that prosecutors will encounter the “representatives of [the doubtful] minority” on which our

criminal system depends. Ibid.

Empirical studies in the wake of Williams have

demonstrated, even under experimental conditions

designed to engender reasonable doubt, that smaller

juries favor conviction at higher rates. In one such

experiment, six-member juries voted to convict nine

out of ten times, while twelve-person juries did so in

11

only two. Valenti & Downing, Six Versus Twelve

Member Juries: An Experimental Test of the Supreme

Court Assumption of Functional Equivalence, 1 Personality & Soc. Psychol. Bull. 273, 274 (1974). Another study confirmed that smaller juries are more

likely to convict in cases for which twelve-person juries might harbor doubts and hang. Roper, Jury Size

and Verdict Consistency: “A Line Has to Be Drawn

Somewhere”?, 14 L. & Soc’y Rev. 977, 990 (1980).

“[B]y permitting criminal juries to be reduced in size,”

Williams “quiets voices of reasonable doubt, potentially leading to more unjust convictions.” Miller, supra, at 674. Undoing Williams, then, would restore

the jury’s role as a check against overreach.

2. The jury’s truth-seeking function also is better

served by having twelve-person juries rather than juries of only six or eight. In the half-century since Williams, studies have shown that the traditional twelveperson jury is better able to process the evidence, arguments, and instructions in a lengthy or complex trial.

More jurors mean more resources to improve reasoning, whether through “recollection of testimony, recognition of inconsistencies, or comprehension of the

court’s instructions.” Kaye, And Then There Were

Twelve: Statistical Reasoning, the Supreme Court, and

the Size of the Jury, 68 Calif. L. Rev. 1004, 1020 (1980);

accord Saks & Marti, A Meta-Analysis of the Effects of

Jury Size, 21 Law & Hum. Behav. 451, 458 (1997) (“the

larger the decision-making group, the better the decisions will be because of the increased resources provided by having more group members”); Carrington,

The Seventh Amendment: Some Bicentennial Reflections, 1990 U. Chi. Legal F. 33, 54 (“larger groups such

as full juries have greater resources of memory and

cognitive understanding . . . and for these reasons

make more accurate factual determinations”).

12

As a result, the traditional twelve-person jury is

“more sensitive to the ‘ambiguities in the case’” that

could produce reasonable doubt. Miller, supra, at 671.

Research bears out that conclusion. “Studies have

demonstrated that seating twelve jurors will result in

a verdict that is a more reliable reflection of the statistical community average.” Su & Goravara, supra,

at 1020. Juries with fewer members, conversely, “are

more likely to produce outlier verdicts inconsistent

with community values.” Ibid.

Relatedly, many studies “have demonstrated that

the quality of the jury’s discussion and deliberation is

better in larger groups than in smaller ones.” Arnold,

Trial by Jury: The Constitutional Right to a Jury of

Twelve in Civil Trials, 22 Hofstra L. Rev. 1, 31 & n.216

(1993) (collecting studies). Twelve-member juries subject the jurors’ initial impressions, memories, and conclusions to “more viewpoints, types of expertise, and

mutually cancelling biases.” Kaye, supra, at 1020; accord Saks & Marti, supra, at 458 (observing “more

substantive deliberation” among twelve jurors, involving “the sharing of more facts, more ideas, and more

challenges to the tentative conclusions of others”). Because of the greater variety of views present, “twelveperson juries facilitate minority resistance to conformity pressure from the majority, promote a more vigorous deliberation of the issues, and deter immediate

decisions in all but the most clear-cut cases.” Miller,

supra, at 673.

The twelve-member jury’s capacity for “better

testing of ideas and reactions” yields “more accurate

factual determinations.” Carrington, supra, at 54.

And improved accuracy shields the innocent from erroneous conviction—without making conviction of the

guilty unduly difficult.

13

3. Finally, juries of twelve better achieve “community participation and shared responsibility” in deciding the guilt of the accused. Williams, 399 U.S. at 100.

“[T]he Sixth Amendment’s promise of a jury of

one’s peers means a jury selected from a representative cross section of the entire community.” Ramos,

590 U.S. at 100 n.47. Twelve-person juries deliver on

that promise more faithfully than six- or eight-person

juries because they are more likely to suitably represent a variety of voices and perspectives. In contrast,

juries with fewer members “threaten to deprive defendants of a fair possibility of obtaining a jury composed of a representative cross-section of the community.” Khorrami v. Arizona, 143 S. Ct. 22, 26 (2022)

(Gorsuch, J., dissenting from denial of certiorari).

Williams itself recognized that a jury must be

sizeable enough that it “provide[s] a fair possibility

for obtaining a representative cross-section of the

community.” 399 U.S. at 100. Yet the Court satisfied

itself with speculation that “the difference between

the 12-man and the six-man jury in terms of the

cross-section of the community represented” was

“likely to be negligible.” Id. at 102.

Eliminating half the opportunity for a fair crosssection is anything but negligible. “[I]f we want individual juries to be cross-sectional, . . . we should want

each jury to be of substantial size.” Amar, Reinventing Juries: Ten Suggested Reforms, 28 U.C. Davis L.

Rev. 1169, 1188 (1995) (emphasis omitted). Twelvemember juries are better able to “draw citizens from

different backgrounds,” ibid., improving the deliberative process and ensuring a broader check on government abuses. Meanwhile, “the smaller the size of the

jury, the less frequently it even approaches community representation.” Zeisel, supra, at 716 (emphasis

14

added). As jury size decreases, the odds that a jury

will not include a juror representing a minority population—racial, ideological, or otherwise—increase

considerably. Saks & Marti, supra, at 457 (“12-person

juries are more likely than 6-person juries to contain

at least one member of whatever minority group is under consideration.”); Arnold, supra, at 30 (discussing

a study showing that 72% of twelve-person juries included minority jurors as compared to 47% of six-person juries).

Excluding minority views undermines the jury’s

representative function in stark ways. With homogeneity, the jury’s deliberative capacities weaken because there is less “competition among views” putting

“ideas and reactions” to a rigorous test. Carrington,

supra, at 54. Lone dissenters—more likely in smaller

juries—are more easily pressured to conform with the

majority. Miller, supra, at 673. Permitting trial by

fewer than twelve jurors thus weakens the bulwark

against “unfounded criminal charges brought to eliminate enemies,” both because it is easier to exclude

sympathetic community members from a smaller

panel and because potential dissenters are less likely

to resist the majority. Duncan, 391 U.S. at 156.

The effect of omitting minority perspectives from

criminal juries is neither accidental, see Pet. Br. 36-37,

nor theoretical. Experience in the decades since Williams reveals the measurable and unsettling impact of

jury homogeneity. One study of over 700 felony jury

trials in Florida found that all-white jury pools yielded

a 16-percentage-point increase in conviction rates for

Black defendants compared to white defendants.

Anwar et al., The Impact of Jury Race in Criminal Trials, 127 Q. J. Econ. 1017, 1019-20, 1027-28, 1034-35

(2012). Meanwhile, that gap was “eliminated” when

15

the jury pool included at least one Black member. Id.

at 1035. Another study similarly demonstrated that

white jurors voted to convict Black defendants less

frequently when part of a racially diverse jury. Sommers & Ellsworth, How Much Do We Really Know

About Race and Juries?: A Review of Social Science

Theory and Research, 78 Chi.-Kent L. Rev. 997, 102829 (2003). By improving cross-sectional representation, twelve-member juries protect against these

harmful outcomes more effectively than their smaller

counterparts.

The harmful effects of six- and eight-person juries

extend well beyond particular cases. Juries are a vital

stand-in for the “community participation in the determination of guilt or innocence” on which the Framers insisted. Duncan, 391 U.S. at 156. Enforcing the

historical jury-trial right is thus “critical to public confidence in the fairness of the criminal justice system,”

Taylor v. Louisiana, 419 U.S. 522, 530 (1975), and “ensures continued acceptance of the laws by all of the

people,” Powers v. Ohio, 499 U.S. 400, 407 (1991). Deviating from that right, and permitting conviction by

a six- or eight-member jury far less likely to contain a

fair cross-section of the community, risks poisoning

the well and increasing public skepticism or even hostility to the criminal system. See Pet. Br. 35-36.

*

*

*

Williams represented both an abandonment of historical wisdom and a “misapplication of social-science

research.” Miller, supra, at 622. These errors combined to “trigger[ ] the ‘unthinkable’ dismantling of an

irrevocable constitutional cornerstone.” Ibid. “Before

the ink dried on the decision” and even more “in the

years since,” social science and experience have confirmed Williams’s errors—and demonstrated how the

16

common law serves the important goals of the jury

system far better than does a jury of fewer. Khorrami,

143 S. Ct. at 26-27 (Gorsuch, J., dissenting from denial of certiorari).

This Court has already undercut Williams to the

point that the decision should “be regarded as retaining

no vitality.” See Herrera v. Wyoming, 587 U.S. 329,

342 (2019). In Ramos, this Court squarely rejected

the same sort of “breezy cost-benefit analysis” that

this Court used in Williams to depart from centuries

of common-law wisdom. Ramos, 590 U.S. at 99-100.

As the Court explained, “[w]hen the American people

chose to enshrine” the jury-trial right “in the Constitution, they weren’t suggesting fruitful topics for future cost-benefit analyses.” Id. at 100. They were instead striving “to ensure that their children’s children

would enjoy the same hard-won liberty they enjoyed.”

Ibid. And there is no doubt what right had been cemented in constitutional text: “‘no person could be

found guilty’” except by “‘the unanimous suffrage of

twelve of his equals and neighbors.’” Id. at 90.

The Court should overrule Williams—if indeed

anything is left of it, see Pet. Br. 24-27—to restore the

jury to its full constitutional vigor.

III. Overruling Williams would not have undue

consequences.

Re-enshrining the twelve-member jury as a constitutional requirement would be minimally disruptive to the state and federal criminal systems. Both

sets of systems are well equipped to hold trials with

twelve jurors, as they already do in most circumstances. Restoring the historical meaning of the Sixth

Amendment would not affect final convictions, and

any small impact on pending cases “cannot outweigh

17

the interest we all share in the preservation of our

constitutionally promised liberties.” Ramos, 590 U.S.

at 110-11 (opinion of Gorsuch, J.).

At the state level, the enormous majority of criminal trials already comport with the historical demands

of the Sixth Amendment. All but seven States generally require a twelve-person jury for serious offenses.

See Pet. Br. 13-14. Even Florida requires twelve jurors, if only in capital cases. Fla. Stat. § 913.10. So

even though a ruling on the Sixth Amendment jurytrial right would apply to all States through the Fourteenth Amendment, Duncan, 391 U.S. at 149, 156-58,

it would only require a system that almost every State

is already using.

Nor would a ruling in petitioner’s favor unduly

disrupt the federal system. There (as in States with

analogous rules), the only permitted departures from

the twelve-person jury are (1) those to which the defendant consents and (2) those involving excusal of a

juror for “good cause” “[a]fter the jury has retired to

deliberate.” Fed. R. Crim. P. 23(b)(2)-(3). The former

is uncontroversial; a defendant with a right to trial by

jury has the corresponding ability to “consent to be

tried by a less number than twelve.” Patton, 281 U.S.

at 290. And the latter is no reason to preserve Williams and the six- and eight-person jury trials it permits. The Court could reserve Rule 23(b)(3) for a case

that presents the issue. See Pet. Br. 13 n.4. Besides,

that rule is limited to rare situations in which a juror

“is seriously incapacitated” or unable to continue, Fed.

R. Crim. P. 23 advisory committee’s notes to 1983

amendments, and those situations are becoming rarer

still now that judges can seat alternates, Fed. R. Crim.

P. 24 advisory committee’s notes to 1999 amendments,

and take advantage of remote deliberations where

18

appropriate, see Rossner & Tait, Virtual Technology

and the Changing Rituals of Courtroom Justice, 98

Chi.-Kent L. Rev. 251, 277 (2023).

Overruling Williams also would not subject final

state or federal convictions by fewer than twelve jurors to belated attack. Any rule reversing Williams

and restoring the twelve-member jury-trial right “will

not be applicable to those cases which have become final before the new rules are announced.” Teague v.

Lane, 489 U.S. 288, 310 (1989). This Court has also

clarified that there is no exception for “watershed”

rules, Edwards v. Vannoy, 593 U.S. 255, 272 (2021),

even when a case restores “the original meaning” of a

constitutional provision, Danforth v. Minnesota, 552

U.S. 264, 270 (2008).

For pending cases, reinstating the historical requirements of the jury-trial right may impose some

additional burdens on criminal systems, but that is an

inherent feature of any new rule of criminal procedure. When, for instance, this Court’s holding that

the Federal Sentencing Guidelines must be only advisory led it to “vacate[ ] and remand[ ] nearly 800 decisions to the courts of appeals,” Ramos, 590 U.S. at 108,

that was a small price to pay for “preserving [the] ancient guarantee” enshrined in the Sixth Amendment,

United States v. Booker, 543 U.S. 220, 237 (2005).

So too here. Whatever minor disruptions may result from overruling Williams are the necessary result

of the balance the Framers struck long ago. “[A]dministrative conveniences,” Baldwin v. New York, 399

U.S. 66, 73 (1970) (plurality opinion), are no justification for flagrant violations of one of the Constitution’s

most cherished rights, Ramos, 590 U.S. at 89. The

Court should once again acknowledge “what we all

19

know to be true about the Sixth Amendment.” Id. at

111 (opinion of Gorsuch, J.).

CONCLUSION

The judgment of the Florida Fourth District Court

of Appeal should be reversed.

Respectfully submitted.

Jonathan D. Hacker

Co-Chair, Supreme Court

Amicus Committee

NATIONAL ASSOCIATION OF

CRIMINAL DEFENSE LAWYERS

1660 L St., NW

Washington, DC 20036

Arjun Ogale

GIBSON, DUNN & CRUTCHER LLP

2001 Ross Ave., Ste. 2100

Dallas, TX 75201

Matt Aidan Getz

Counsel of Record

Kahn A. Scolnick

Patrick J. Fuster

Paige H. Petrashko

GIBSON, DUNN & CRUTCHER LLP

333 South Grand Ave.

Los Angeles, CA 90071

(213) 229-7754

mgetz@gibsondunn.com

Tate Rosenblatt

GIBSON, DUNN & CRUTCHER LLP

1700 M St. N.W.

Washington, DC 20036

Counsel for Amicus Curiae

August 13, 2026