Encyclopedia of Psychology and Law

equivalence between large and small juries, but it now

held that juries smaller than 6 were unconstitutional

because, in Justice Blackmun’s opinion, the studies

raised serious concerns about the performance of

juries of fewer than 6 members.

The research findings have been recognized in

other legal settings. The Standing Committee on

Federal Civil Rules recommended 12-person juries

for federal civil trials (a recommendation not adopted

by the Judicial Conference). During the administra-

tion of President Reagan, the Department of Health

and Human Services promulgated a model medical

malpractice statute for the states that specified

12-person juries (specifically for their greater pre-

dictability). And the New Hampshire Supreme Court—

citing the factual findings of Ballewbut rejecting its

legal holding—ruled that a reduction in jury size below

12 would violate the New Hampshire State Constitution

(which similarly did not specify a jury size).

Social Decision Rule

From the 14th century in England until the latter part

of the 20th century, juries had been required to reach

unanimous verdicts. Several American states began to

permit quorum verdicts, and in the 1970s, challenges

to the constitutionality of quorum verdicts came

before the U.S. Supreme Court.

The principal motivation for eliminating the una-

nimity rule seems to have been a desire to reduce the

incidence of hung juries. Without quorum verdicts,

hung juries occur at a national rate of about 5% or 6%,

and allowing quorum verdicts reduces that rate by a

few percentage points.

In Apodaca v. Oregon (1972) and Johnson v.

Louisiana(1972), the Supreme Court held verdicts

split as widely as 9:3 to be constitutional, and in

Burch v. Louisiana(1979), the Court held that the

verdicts of 6-person juries had to be unanimous. The

Court’s reasoning was much the same as in the jury-

size cases: As to the social decision rule for a jury

verdict, the Constitution does not say and the inten-

tions of the framers are unknown, so the “inquiry

must focus upon the function served by the jury in

contemporary society.”

The main issues about group behavior that were

debated in the Court’s functional analysis were

whether juries required to reach only quorum deci-

sions would pay less attention to the arguments of the

unneeded minority, whether the jury’s verdicts would

be less accurate, and whether the weight of evidence

sufficient to produce a conviction would be reduced.

The last of those questions is an especially interesting

one. The standard or proof (preponderance, beyond a

reasonable doubt) is directed at individual jurors,

seemingly separate from the issue of the rules for com-

bining individual views into a group decision. But the

two together will surely have a bearing on the group’s

collective confidence in their verdict and on the quan-

tum of proof needed to lift the jury over those several

individual-to-group decision thresholds to a verdict.

The Supreme Court’s opinions assert that jurors

will not behave differently when a nonunanimous

decision rule is in place—at least not when the jury

numbers 12—or not differently enough to matter. Less

research has been done on social decision rules than

on group sizes, but what research has been conducted

does not generally support the Court’s majority.

Compared with unanimous rule juries, juries oper-

ating under a nonunanimous decision rule deliberate

for a shorter time, do not let dissenters have sufficient

say so as to change the minimum consensus once it is

achieved (while in unanimous rule juries, jurors in the

minority participate disproportionately in the deliber-

ation), are more vote oriented and less evidence ori-

ented, are less certain of the defendant’s guilt when

convicting, and are less likely to end in a deadlock. In

research on group decision making generally, groups

required to reach unanimous decisions are found to be

more likely to reach correct solutions (on problems

with clear right/wrong answers) than groups working

with less-demanding social decision rules.

Notwithstanding the Supreme Court’s rulings per-

mitting nonunanimous verdicts under the federal

Constitution, the great majority of states continue to

require unanimous verdicts in felony trials, and all do

in capital murder trials.

Michael J. Saks

See alsoJury Deliberation; Jury Reforms; U.S. Supreme

Court

Further Readings

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

Arnold, R. S. (1993). Trial by jury: The constitutional right to a

jury of twelve in civil trials. Hofstra Law Review, 22,1–35.

Ballew v. Georgia, 435 U.S. 223 (1978).

Burch v. Louisiana, 441 U.S. 130 (1979).

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