Jury selection is the selection of the people who will serve on a jury during a jury trial. The group of potential jurors (the "jury pool,” also known as the venire) is first selected from among the community using a reasonably random method. Jury lists are compiled from voter registrations and driver license or ID renewals. From those lists, summonses are mailed. A panel of jurors is then assigned to a courtroom.

The prospective jurors are randomly selected to sit in the jury box. At this stage, they will be questioned in court by the judge and/or attorneys in the United States. Depending on the jurisdiction, attorneys may have an opportunity to mount a challenge for cause argument or use one of a limited number of peremptory challenges.

In some jurisdictions that have capital punishment, the jury must be death-qualified to remove those who are opposed to the death penalty. Jury selection and techniques for voir dire are taught to law students in trial advocacy courses. However, attorneys sometimes use expert assistance in systematically choosing the jury via a process of scientific jury selection, although other uses of jury research are becoming more common. The jury selected is said to have been "empaneled".

Selected jurors are generally subjected to a system of examination whereby both the prosecution (or plaintiff, in a civil case) and defence can object to a juror. In common law countries, this is known as voir dire. Voir dire can include both general questions asked of an entire pool of prospective jurors, answered by means such as a show of hands, and questions asked of individual prospective jurors and calling for a verbal answer. In some jurisdictions, the attorneys for the parties may question the potential jurors; in other jurisdictions, the trial judge conducts the voir dire.

The method and scope of the possible rejections varies between countries:

In the United States the process of voir dire is often much more in-depth than in other countries and its practical implementation is somewhat controversial because of this. The amount of privacy that the potential jurors are afforded when asked questions raises the issue of the definition of "impartial jury". Some people^[who?] are skeptical as to whether the intensive questioning of potential jurors looks not just for inherent bias but for a potential to be emotionally swayed. On the other hand, proponents argue that this method gives both sides more confidence in the verdict.

Generally, the prosecution and the defense want the maximum amount of information about the jurors, so that they can estimate which people are most likely to be sympathetic to their case. Although the practice is opposed by the American Bar Association in their "Standards on Juror Use and Management", prosecutors, defense attorneys, and news media can in most cases legally take some of the information jurors disclose, such as their home addresses, and use it to investigate the jurors outside the court through such means as running criminal background checks or simply driving past the jurors' homes to see what information they can glean from its appearance. These independent investigations usually happen without any notice to the jurors, the court, or other parties in the case.

Part XX of the Criminal Code of Canada allows for a jury in a Canadian murder trial to consist of twelve jurors. However, a minimum of ten jurors and a maximum of 14 jurors may hear the evidence for a trial. At the end of the trial, a maximum of twelve jurors and a minimum of ten jurors may deliberate.