Early English jurors were chosen because they already knew the facts
Medieval English juries were not neutral strangers. Jurors were recruited from the neighbourhood of a dispute precisely because they were expected to know what had happened before they ever came to court. Today's idea of an impartial jury weighing evidence it hears for the first time came much later.
Groups of local men investigating crimes were an old Germanic custom, and around 997 King Æthelred decreed at Wantage that the twelve leading thegns of each hundred should swear not to accuse the innocent or shield the guilty. In Normandy before 1066, juries of nobles settled land disputes so the duke need not judge his own case. Under Henry II, the Assize of Clarendon in 1166 spread juries of presentment across England, local men testifying under oath about crimes nearby. Sheriffs gathered cases and jurors, and royal justices ran trials, letting the king delegate without handing out too much power.
A turning point came in 1215, when the Church withdrew its blessing from trial by ordeal. Judges already accustomed to quizzing jurors about facts simply began asking whether they found the accused guilty. Much older precedents existed too: jury courts in Athens date back to about 500 BCE, voted by secret ballot and eventually gained power to strike down unconstitutional laws.
Selection gradually became fairer. A 1730 act required parishes to post lists of everyone liable to serve and to draw panels by lot, making it harder for the middle classes to bribe their way out. Local discretion lingered, though: butchers were kept off Essex juries in the eighteenth century, and travelling ice cream sellers were not summoned in summer as late as 1923. In the American colonies, grand juries became tools of resistance, indicting British soldiers and refusing to charge critics of the Crown.
Modern trial juries typically have up to 15 members and may need unanimity or a majority; one that cannot agree is hung. American federal grand juries of 16 to 23 decide whether charges should go to trial. Most civil law countries rely on judges instead, sometimes sitting with lay members.
Source: Jury
