The Weiss et al. v. United States case in 1939 revolved around the issue of whether or not a warrantless search and seizure conducted by federal agents was constitutional under the Fourth Amendment, which protects against unreasonable searches and seizures. The defendants, Weiss and others, were convicted for conspiracy to defraud the United States through mail fraud after evidence obtained from a warrantless search was used against them in court. They appealed their conviction on grounds that this violated their Fourth Amendment rights. However, the Supreme Court upheld their convictions with an unanimous decision stating that while generally warrants are required for searches and seizures under normal circumstances; exceptions can be made when there is probable cause to believe that criminal activity is taking place - as it happened in this case where agents had strong reasons to suspect ongoing mail fraud operation at defendant's premises. This ruling significantly impacted future cases involving similar issues by setting precedent about what constitutes 'probable cause' allowing warrantless searches thereby shaping interpretation of fourth amendment protections.

The dissenting opinion in the case of Weiss et al. v. United States argued that the majority's decision violated the defendants' Sixth Amendment rights to a fair trial by an impartial jury. The dissenting justices believed that, because some members of the jury had been exposed to prejudicial pretrial publicity about the defendants, they could not be considered impartial. They also disagreed with how these jurors were questioned during voir dire, arguing it was insufficient for determining their potential bias or prejudice against the defendants due to exposure from media coverage and public sentiment surrounding this high-profile case. Furthermore, they contended that any juror who admitted having formed an opinion on guilt should have been automatically disqualified rather than being allowed to serve after simply affirming their ability to set aside such opinions and decide based solely on evidence presented at trial.