Jury
Trial jury size

As the concept of a jury was spread through the British Empire, first to Ireland and then to other countries, the size of the jury was one of the details that was adapted to the local culture. The tradition in England was to have twelve jurors, but other countries use smaller juries, and some, such as Scotland, use larger juries.

The size of the jury is to provide a "cross-section" of the public. In Williams v. Florida, 399 U.S. 78 (1970), the Supreme Court of the United States ruled that a Florida state jury of six was sufficient, that "the 12-man panel is not a necessary ingredient of "trial by jury," and that respondent's refusal to impanel more than the six members provided for by Florida law "did not violate petitioner's Sixth Amendment rights as applied to the States through the Fourteenth." In Ballew v. Georgia, 435 U.S. 223 (1978), the Supreme Court ruled that the number of jurors could not be reduced below six.

In Brownlee v The Queen (2001) 207 CLR 278, the High Court of Australia unanimously held that a jury of 12 members was not an essential feature of "trial by jury" in section 80 of the Australian Constitution.

In Scotland, a jury in a criminal trial consists of 15 jurors, which is thought to be the largest in the world. In 2009 a review by the Scottish Government regarding the possibility of reduction led to the decision to retain 15 jurors, with the Cabinet Secretary for Justice stating that after extensive consultation, he had decided that Scotland had got it "uniquely right". Trials in the Republic of Ireland which are scheduled to last over 2 months can, but do not have to, have 15 jurors.

A study by the University of Glasgow suggested that a civil jury of 12 people was ineffective because a few jurors ended up dominating the discussion, and that seven was a better number because more people feel comfortable speaking, and they have an easier time reaching a unanimous decision.
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