In a criminal case, the government prosecutes or charges a defendant with a violation of the criminal law and begins proceedings (bail hearings, arraignments and trials) to prove that charge beyond a reasonable doubt.
The Sixth Amendment provides many protections and rights to a person accused of a crime. One right is to have his or her case heard by an impartial jury—independent people from the surrounding community who are willing to decide the case based only on the evidence. In some cases where there has been a significant amount of news coverage, the Supreme Court has ruled that jury members may be picked from another location in order to ensure that the jurors are impartial.
When choosing a jury, both prosecutors and defense attorneys may object to certain people being included. Some of these objections, called challenges, are for cause (the potential juror has said or done something that shows he or she may not act fairly). Others are peremptory (no real reason need be given, but one side does not want to have that person serve). Lawyers cannot use peremptory challenges to keep people off a jury because of race or gender. – The United States Constitution, What It Says, What It Means, A Hip Pocket Guide