A person facing criminal charges can have either a jury trial or a bench trial. Depending upon the nature of the charges and facts of the case, it may be wise to opt for one type of trial or another.
In a jury trial, members of the community determine a person’s guilt or innocence. In most criminal trials, there is a jury of 12 citizens, and some number of alternate jurors. The purpose of the alternates is to take the place of a juror who has to leave during the case due to an emergency such as illness or a death in the family, so that the trial need not be redone. The jury selection process, called voir dire, involves the defendant and their attorney, the prosecution, and the judge selecting the jurors and alternates from a larger panel of possible jurors. The goal of the defense is to pick the most favorable jury possible, and that is done by asking the jurors questions to weed out those who would be biased or otherwise unfavorable. The defense and the prosecution each get a set number of peremptory challenges (strikes), which is where a prospective juror can be excluded without having to give a reason for doing so. The number of peremptory strikes that each side gets depends upon the nature of the charges, with more serious cases allowing more peremptory challenges. The selected jury hears the evidence, is given instructions by the judge, and at the end of their deliberations determine whether the state has proven the defendant guilty beyond a reasonable doubt. The jury, as the finder of fact, decides what to believe and what to disbelieve.
In a bench trial, the judge fills the role that would normally be handled by a jury. As the finder of fact, the judge decides what to believe and determines whether the state has proven the defendant guilty beyond a reasonable doubt. In some states, there are some criminal charges where there is not a right to a jury trial (e.g. a simple misdemeanor in Iowa), meaning that the case will proceed only to a bench trial.
The defendant is the one who has the right to a jury trial, and only the defendant can decide whether to exercise that right (and have a jury trial) or waive that right (and have a bench trial). A variety of factors should be considered by a defendant and their attorney before the defendant decides whether to have a jury or bench trial. Some cases tend to be thought of as better to try to a jury, while for others there is often a preference in favor of a bench trial. The makeup of the jury pool, the expected judge who would preside at a bench trial, and many other factors must be weighed. That decision is an important one that a defendant is wise to make in consultation with their attorney, but ultimately only the defendant can make the decision.