During voir dire, potential jurors are questioned by attorneys and the judge. It has been argued that voir dire is often ineffective at detecting juror bias. Extended voir dire in major controlled substance trials may increase accuracy in predicting individual verdicts from 50% to 78%.
Each U.S. state has its own system, which is subject to the requirements of the U.S. Constitution.
Constitution
Impartiality Clause
Vicinage Clause
Federal criminal petit juries are required to be composed of residents of the state and federal judicial district wherein the crime was committed, which district shall have been previously ascertained by law.
Faults within the jury selection process
The juror selection process holds the potential for discrimination in the selection of jurors and the final composition of juries. Claims that errors were made during jury selection are among the most common of all grounds for criminal appeals. With regard to legal proceedings within the U.S. military, one argument has been advanced that selection of juries for courts-martial is subject to too much control by commanders, who can pick jurors who will be most likely to convict and hand down heavy penalties. Batson v. Kentucky, banned peremptory challenges based solely on race, although the U.S. Supreme Court has since acted to mitigate its impact. The issue of racial bias in jury selection has been complicated by the question of whose rights are implicated; the prospective juror's, or the defendant's. A Michigan Law Review article, published in 1978, asserted that young people, during that period, were under-represented on the nation's jury rolls. A 2012 study from Duke University published in the Quarterly Journal of Economics investigated the effect of jury selection and racial composition on trial outcomes. The study found that black defendants are significantly more likely than whites to be convicted when there are no potential black jurors in the pool. Even with only one black member of the jury pool, conviction rates are almost identical. While 64% of cases had at least one black potential juror in the pool, only 28% of all trials had one or more black members on the seated jury. "Whenever attorneys use peremptory challenges to strike black members of the pool... they forgo the possibility of excluding another potential juror with a similar ex ante probability of convicting," and the composition of the jury indirectly reflects that of the juror pool. A 2018 study published in the University of Illinois Law Review found that prosecutors and judges tend to remove more African-Americans while defense attorneys remove more whites. As of 2014, the 9th Circuit Court of Appeals has held that a peremptory challenge based on perceived sexual orientation is unconstitutional.
