Peremptory challenge

A peremptory challenge is a right during voir dire (the process of selecting a jury) to reject a certain number of potential jurors without having to give a reason. The word "peremptory" means without a reason given; allowing no contradiction or refusal. Peremptory challenges may be made by either party to the proceedings. This kind of challenge has been more difficult to use because the Supreme Court of the United States has prohibited peremptory challenges (also called peremptory strikes) based on gender or race. Different jurisdictions allow different numbers of peremptory challenges to each side. Some jurisdictions allow additional peremptory challenges. In United States federal courts each side is allowed three peremptory challenges. Also, if there are more than two parties involved in the proceeding the court may allow additional challenges or restrict the number for all parties.
Peremptory vs for cause.
To insure an impartial jury, during voir dire, prospective jurors are questioned by the lawyers and the court. Either lawyer may challenge a juror for cause. Reasons may include the prospective juror's opinions on issues, personal knowledge of the case, their occupation or any reason to believe the juror may not be able to be fair. Unlike peremptory challenges, challenges for cause may not be limited to a certain number in most jurisdictions. The reason for either type of challenge is that each lawyer is trying to find jurors who are sympathetic to their case.
History.
The peremptory challenge has its roots in Roman law. Both parties would propose up to 100 prospective jurors, then each could strike 50. This left a total of 100 jurors on the jury. In English common law, a prosecutor had an unlimited number of peremptory challenges while the defendant has 35. In 1305, the Parliament of England eliminated all peremptory challenges for the prosecution. In 1988, Parliament eliminated all peremptory challenges for the defense. Peremptory challenges came to the United States with the colonists and Common Law. Peremptory challenges remained much the same until the late 20th century.
Peremptory challenges and the Supreme Court.
The following observation is attributed to Mark Twain:
While the right to use peremptory challenges is not guaranteed by the Constitution of the United States, The Supreme Court has held peremptory challenges are "to assure the parties that the jurors before whom they try the case will decide on the basis of the evidence placed before them, and not otherwise."
Three Supreme Court decisions have shaped the modern peremptory challenge: