In Rosales-Lopez v. United States, the Supreme Court considered whether a trial court's refusal to question potential jurors about racial or ethnic bias during voir dire was grounds for overturning a conviction. The defendant, of Mexican descent, had been convicted of smuggling illegal aliens into the U.S., and his counsel requested that prospective jurors be questioned on possible prejudice against Mexicans. The judge denied this request and the Ninth Circuit affirmed his conviction. However, upon reaching the Supreme Court in 1980, it held that under federal law while there is no obligation to inquire into racial or ethnic prejudice in every case involving a defendant of minority status; such an inquiry should be made when circumstances suggest a significant likelihood that racial or ethnic prejudice might affect jury deliberations. In this particular case though, because there were no special factors suggesting higher risk of racial or ethnic bias influencing juror decision-making process beyond what would normally exist whenever a member from any race/ethnicity is on trial - therefore not requiring questioning about such biases - Rosales-Lopez’s conviction was upheld.

In the dissenting opinion for Rosales-Lopez v. United States, Justice William Rehnquist argued that there was no constitutional requirement to ask potential jurors about racial or ethnic bias in every case involving a defendant of a different race or ethnicity. He contended that such an obligation would place an undue burden on the court system and could potentially lead to unnecessary delays and complications in trials. Furthermore, he suggested that it might even encourage prejudice by implying its existence where none may have been present before. Instead, he believed it should be left up to the discretion of trial judges as they are best positioned to determine when such questions are necessary based on their understanding of local conditions and attitudes.