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Jury Unanimity

For much of its history, the American criminal jury has been required to reach unanimous verdicts. In 1972, in a pair of U.S. Supreme Court cases, the Justices held that Sixth and Fourteenth Amendments did not require jury unanimity in state court jury trials. Social science research conducted on the impact of jury unanimity raises questions about the Justices’ assumptions about how non-unanimous decision rules would affect the functioning of the jury. Recent certiorari petitions have pressed the Court to reconsider the jury unanimity issue in light of changing Sixth Amendment jurisprudence and the social science evidence.

Social Science and Law

That all members of the jury must agree unanimously on a final verdict has long been a traditional feature of trial by jury. Consider this set of clips of famous cinematic depictions of trial by jury, where the unanimity requirement creates memorable dramatic tension.

Case Excerpts. In a remarkable departure from the historical tradition, in Apodaca v. Oregon, 406 U.S. 404 (1972), and a companion case, the US Supreme Court held that the Sixth and Fourteenth Amendments did not require jury unanimity in state court jury trials. A plurality of the Court employed a functional rather than a historical test, and concluded that the prime functions of the jury would not be impaired if states required less-than-unanimous jury verdicts.

Excerpt of Apodaca v Oregon

Apodaca v. Oregon, 406 U.S. 404 (1972)

From Justice White’s opinion:

Our inquiry must focus upon the function served by the jury in contemporary society. Cf. Williams v. Florida, supra, at 99-100. As we said in Duncan, the purpose of trial by jury is to prevent oppression by the Government by providing a "safeguard against the corrupt or overzealous prosecutor and against the compliant, biased, or eccentric judge." Duncan v. Louisiana, 391 U.S. at 156….A requirement of unanimity, however, does not materially contribute to the exercise of this common sense judgment. As we said in Williams, a jury will come to such a judgment as long as it consists of a group of laymen representative of a cross-section of the community who have the duty and the opportunity to deliberate, free from outside attempts at intimidation, on the question of a defendant's guilt. In terms of this function, we perceive no difference between juries required to act unanimously and those permitted to convict or acquit by votes of 10 to two or 11 to one. Requiring unanimity would obviously produce hung juries in some situations where nonunanimous juries will convict or acquit*. But in either case, the interest of the defendant in having the judgment of his peers interposed between himself and the officers of the State who prosecute and judge him is equally well served…..Petitioners also cite quite accurately a long line of decisions of this Court upholding the principle that the Fourteenth Amendment requires jury panels to reflect a cross-section of the community….. We also cannot accept petitioners' … assumption -- that minority groups, even when they are represented on a jury, will not adequately represent the viewpoint of those groups simply because they may be outvoted in the final result. They will be present during all deliberations, and their views will be heard.

*The most complete statistical study of jury behavior has come to the conclusion that when juries are required to be unanimous, ‘the probability that an acquittal minority will hang the jury is about as great as that a guilty minority will hang it.’ H. Kalven & H. Zeisel, The American Jury 461 (1966).

Excerpt of Johnson v. Louisiana

Johnson v. Louisiana 406 U.S. 356 (1972)

JUSTICE WHITE delivered the opinion of the Court.

Under both the Louisiana Constitution and Code of Criminal Procedure, criminal cases in which the punishment is necessarily at hard labor are tried to a jury of 12, and the vote of nine jurors is sufficient to return either a guilty or not guilty verdict. The principal question in this case is whether these provisions allowing less than unanimous verdicts in certain cases are valid under the Due Process and Equal Protection Clauses of the Fourteenth Amendment…. Appellant focuses instead on the fact that less than all jurors voted to convict, and argues that, because three voted to acquit, the reasonable doubt standard has not been satisfied, and his conviction is therefore infirm….. But the mere fact that three jurors voted to acquit does not, in itself, demonstrate that, had the nine jurors of the majority attended further to reason and the evidence, all or one of them would have developed a reasonable doubt about guilt. We have no grounds for believing that majority jurors, aware of their responsibility and power over the liberty of the defendant, would simply refuse to listen to arguments presented to them in favor of acquittal, terminate discussion, and render a verdict. On the contrary, it is far more likely that a juror presenting reasoned argument in favor of acquittal would either have his arguments answered or would carry enough other jurors with him to prevent conviction. A majority will cease discussion and outvote a minority only after reasoned discussion has ceased to have persuasive effect or to serve any other purpose when a minority, that is, continues to insist upon acquittal without having persuasive reasons in support of its position….Appellant offers no evidence that majority jurors simply ignore the reasonable doubts of their colleagues or otherwise act irresponsibly in casting their votes in favor of conviction, and before we alter our own longstanding perceptions about jury behavior and overturn a considered legislative judgment that unanimity is not essential to reasoned jury verdicts, we must have some basis for doing so other than unsupported assumptions.

Justice Douglas’s dissent in Johnson v. Louisiana:

The plurality approves a procedure which diminishes the reliability of a jury. First, it eliminates the circumstances in which a minority of jurors (a) could have rationally persuaded the entire jury to acquit, or (b) while unable to persuade the majority to acquit, nonetheless could have convinced them to convict only on a lesser-included offense. Second, it permits prosecutors in Oregon and Louisiana to enjoy a conviction-acquittal ratio substantially greater than that ordinarily returned by unanimous juries.

The diminution of verdict reliability flows from the fact that nonunanimous juries need not debate and deliberate as fully as must unanimous juries. As soon as the requisite majority is attained, further consideration is not required either by Oregon or by Louisiana even though the dissident jurors might, if given the chance, be able to convince the majority. Such persuasion does in fact occasionally occur in States where the unanimous requirement applies: ‘In roughly one case in ten, the minority eventually succeeds in reversing an initial majority, and these may be cases of special importance.’*  One explanation for this phenomenon is that because jurors are often not permitted to take notes and because they have imperfect memories, the forensic process of forcing jurors to defend their conflicting recollections and conclusions flushes out many nuances which otherwise would go overlooked. This collective effort to piece together the puzzle of historical truth, however, is cut short as soon as the requisite majority is reached in Oregon and Louisiana. Indeed, if a necessary majority is immediately obtained, then no deliberation at all is required in these States. (There is a suggestion that this may have happened in the 10-2 verdict rendered in only 41 minutes in Apodaca's case.) To be sure, in jurisdictions other than these two States, initial majorities normally prevail in the end, but about a tenth of the time the rough-and-tumble of the jury room operates to reverse completely their preliminary perception of guilt or innocence. The Court now extracts from the jury room this automatic check against hasty fact-finding by relieving jurors of the duty to hear out fully the dissenters. It is said that there is no evidence that majority jurors will refuse to listen to dissenters whose votes are unneeded for conviction. Yet human experience teaches that polite and academic conversation is no substitute for the earnest and robust argument necessary to reach unanimity.

* H. Kalven & H. Zeisel, The American Jury 490 (1966). See also The American Jury: Notes For an English Controversy, 48 Chi.B.Rec. 195 (1967)

Justice Douglas included the following table, taken from Kalven & Zeisel’s The American Jury, in his dissenting opinion in Johnson. He used it to support the claim that the nonunanimous verdict option favored the state over the defendant. How persuasive is this table?

Last Vote of Deadlocked Juries
Vote for Conviction
Per Cent
 Number of juries in sample: 48

Social Science Critique:

A flurry of jury research, much of it mock jury style experiments conducted during the 1970s, investigated the claim that jury functioning was similar in juries operating under unanimous and less-than-unanimous decision rules.

Much of that research found significant differences in jury deliberations.

More recent research with actual juries also finds differences. Consider the following research project. Do the results lend more support to Justice White or Justice Douglas in their competing assertions about how juries are influenced by the unanimity requirement?

National Center for State Courts publication, Are Hung Juries a Problem? (felony jury trial project)

Recently, a new line of legal attack has been mounted, taking advantage of contemporary developments in Supreme Court jurisprudence over jury trial rights, and relying as well on the body of empirical research showing differences in the operation of juries deliberating under the two types of decision rules.

For FuRther Study

Legal Documents:
Classic cases:

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New developments:

Social Science Materials

  • Harry Kalven, Jr. & Hans Zeisel, The American Jury (1966). This book was cited by both plurality and dissenting opinions in Apodaca and Johnson, to support different propositions. It was the first large-scale systematic study of American juries.
    • Scan of relevant pages?
  • Consider White’s opinion in Apodaca: “The most complete statistical study of jury behavior has come to the conclusion that, when juries are required to be unanimous, "the probability that an acquittal minority will hang the jury is about as great as that a guilty minority will hang it." H. Kalven & H. Zeisel, The American Jury 461 (1966).” Contrast with Justice Douglas’s assertion that the allowance of nonunanimous decisions will favor the state.  Now consider the link between first votes and final verdicts in a large study of felony juries [adapted from Hannaford et al., fig. 5.2]


  • The table above is taken from a large-scale study of hung juries, conducted by the National Center for State Courts with National Institute of Justice funding. See the full report: Are Hung Juries a Problem? (felony jury trial project)
  • How often do juries agree unanimously when they are not required to do so? The answer may surprise you. On the Frequency of Non-Unanimous Felony Verdicts in Oregon. (2009) by the Oregon Public Defenders Office.


Additional Materials (Popular, Audio, Video)

  • Even though Former Illinois Gov. Rod Blagojevich was only found guilty on one of 24 charges, he was just one vote shy of being convicted on some of the more serious charges. Professor Valerie Hans talks with PBS NewsHour's Jim Lehrer about the jury system and the dynamics of a jury's deliberations. Link at:
  • Findlaw column by Sherry Colb, Ten Angry Men: Why the Supreme Court Should Take a Jury Unanimity Case (2009). Link at:
  • New York Times columnist Adam Liptak writes about jury unanimity: “Guilty by a 10-2 vote?” He begins: “Twelve Angry Men” might have been a much shorter movie had it been set in Oregon. Instead of letting Juror No. 8, the lone holdout played by Henry Fonda, methodically convince his fellow jurors that there was good reason to doubt the defendant’s guilt, an Oregon jury might have just voted and been done with it….” Link to his article at:
  • Oregon Public Broadcasting: show on jury deliberations
  • ABA President – open letter encouraging US Supreme Court to take the jury unanimity challenge in Bowen. v. Oregon
  • ABA President – open letter encouraging US Supreme Court to take the jury unanimity challenge in Bowen. v. Oregon.
  • Non-unanimous jury verdicts in felony trials are only allowed in Oregon and Louisiana. Alongside Professor Aliza Kaplan, three first year law students from Lewis & Clark Law School submitted this amicus curiae brief asking the Supreme Court to consider the constitutionality of non-unanimous jury verdicts in felony cases. Focus on Non-unanimous Juries in Oregon: CIRC Files Amicus Brief, Lewis & Clark Law School (Sep. 17, 2017). See the petition for a writ of certiorari for more details about the case, Lambert v. Louisiana, which the Supreme Court ultimately declined to hear.
  • This Slate article discusses the impact of Florida's former non-unanimous jury rule in capital sentencing, which was held unconstitutional by the Florida Supreme Court in October, 2016. Larry Hannan, Death by Non-unanimous Jury, Slate (Mar. 16, 2017, 6:48 P.M.).