A law court or 'petit' jury (hereafter 'jury') is a randomly selected group of citizens of a country sworn in to participate in deliberation for the rendering of a verdict on behalf of the government.
Problems and Purpose
The primary purpose of a court jury is to deliberate and come up with a conclusion based on the evidence and witnesses provided. Juries exists to prevent “oppression by the government," which is supported by the presumption of innocence.
Juries are not meant to make assumptions about topics not brought up by either the defence or prosecution, but rather make their conclusion/verdict based on information provided. They cannot use their own judgments and opinions. In the United States, each selected juror goes through voir dire, meaning “to say the truth”, in order to make sure that there are no links between jurors and people involved in the trial. For example, a person who was preliminarily selected to be part of a jury will be disqualified or removed if they know the defendant or plaintiff. Lawyers generally want juries who are not legally educated, as juries who don't know the legal systems are more easily manipulated. Furthermore jurors that have too much legal knowledge might be disqualified from participating.
Origins and Development
Juries date back to ancient Greece. For instance, the famous trial of Socrates' involved higher status citizens expressing concerns for Athenian youth because they thought Socrates was corrupting them. There were anywhere from six to 501 members of the jury.
In Great Britain in the 14th century, a jury had to reach unanimous decision in criminal cases with 12 members. It was common to incarcerate the jury without food and water until verdict was reached. Jurors were prosecuted if later evidence demonstrated error in verdict. In 1852, Lord Chief Justice Loke developed choosing a jury as it is today.
Participant Recruitment and Selection
The US Constitution provides the 6th amendment which entitles citizens the right to a jury trial. Juries must have 6-12 members, as less than 6 is unconstitutional. In civil courts, there are usually six members and in criminal courts, there are usually twelve members. However, this number will differ from country to country and in different court structures. The jury is selected from different demographics to represent a country, state or city.
How it Works: Process, Interaction and Decision-Making
As Dr. John Gastil noted in his book, Political Communication and Deliberation, jurors do deliberate fairly well. Most of the deliberation happens in the court when jurors listen to evidence and witnesses. The assertion of self-deliberation then reestablishes in the jury room when jurors began to deliberate.
Robert Goodin, an Australian philosopher, documented that jurors start deliberating within as they watch a trial. So even before coming into the room to deliberate as a group, they already have a sense of the verdict. One of the findings about jurors is that 90% of the time they already have deliberated and have a good idea of the verdict as they process each evidence and witness on the spot 
There are two distinct deliberation processes: one is verdict-driven while the other is evidence-driven. Most cases are evidence driven deliberation where the jury is actually going piece by piece, evidence by evidence, and witness by witness to come to the conclusion. In contrast, for verdict driven, the deliberation views how many jurors have arrived at a verdict.
Influence, Outcomes, and Effects
Know what outcomes and effects this method typically has? Help us complete this section!
Analysis and Lessons Learned
Want to contribute an analysis of this method? Help us complete this section!
Bray, R. and Noble, A. (1978). Authoritarianism and Decisions of Mock Juries: Evidence of Jury Bias and Group Polarization. Journal of Personality and Social Psychology 36(12), pp. 1424-1430
Gastil, J., Deess, E.P., Weiser, P.J. and Simmons, C. (2010). The Jury and Democracy. New York: Oxford University Press.
Hans, V. and Vidmar, N. (1986). Judging the Jury. Plenham Press.
Hastie, R., Penrod, S. and Pennington, N. (2002). Inside the Jury. New Jersey: The Lawbook Exchange Ltd.