Juries In-depth: Jury Decision Making

Size and unanimity requirements

Criminal cases   

The Supreme Court has held under the Sixth Amendment that juries in criminal cases are not required to be the traditional size of twelve persons (although they cannot consist of less than six persons).  Nonetheless, all federal criminal cases use a twelve-person jury, and only a handful of states allow juries of less than twelve for felony trials, although as to misdemeanor cases states are about evenly split between those that require twelve-person juries and those that provide for smaller juries (typically six persons). 

The Supreme Court has also held that a guilty verdict from a twelve-person jury need not be unanimous (nine votes is constitutionally permissible), although if the jury consists of only six persons, unanimity is required.  Nonetheless, federal statutes require a unanimous verdict in both felony and misdemeanor federal cases.  All states except Louisiana and Oregon require unanimous verdicts in felony cases, while only Oregon permits a non-unanimous verdict in misdemeanor cases.

Civil cases in federal court

The Seventh Amendment right to a jury trial does not require either a twelve-person jury or a unanimous verdict.  Federal statutes provide for a six-person unanimous verdict in most civil cases. 

Civil cases in state court

Size and unanimity requirements in civil cases vary considerably under state laws.  Less than half the states require twelve-person juries, and about half the states allow for non-unanimous verdicts.

For the Supreme Court cases establishing the principles of law set forth above, click here.

For a detailed listing (current as of 1998) of the size and unanimity requirements of all American jurisdictions, click here and scroll to Table 42: Trial Juries: Size and Verdict Rules.

Social science research indicates that the size and unanimity requirements make some difference in how juries go about making decisions. A relatively recent article reviews all the social science research studies on the effects of eliminating the rule of unanimity, and concludes,  “there may only be a small range of evidence in which decision rule [of unanimity] effects consistently appear (i.e. when the prosecution/plaintiff’s case is not particularly weak or strong).”  See, Dennis J. Devine, et al., "Jury Decision Making: 45 Years of Empirical Research on Deliberating Groups," 7 Psychology, Pub. Pol. & L.  622 (2001).  That same article examines social science research on the effects of reducing jury size from the traditional 12, and concludes that in criminal cases smaller juries took significantly less time to deliberate; participation tended to be less and more variable; larger juries were more likely to contain a racial or ethnic minority; 12-person juries hung less often; and 12-person juries were no more likely to arrive at the “correct” outcome as defined by a majority of the population surveyed.  Social science research regarding jury size in civil cases was too inconclusive to warrant drawing any conclusions.