In Quercia v. United States, the Supreme Court ruled in favor of the defendant, overturning his conviction for tax evasion due to judicial misconduct during trial. The judge had instructed the jury that they could consider any changes in Quercia's demeanor while testifying as evidence of guilt. This instruction was deemed inappropriate because it suggested a presumption of guilt and interfered with the jury's role as fact-finder by encouraging them to make assumptions about credibility based on demeanor alone. Furthermore, after closing arguments but before deliberation began, the judge expressed personal belief in Quercia’s guilt which further violated his right to a fair trial by an impartial jury. Therefore, these actions were found prejudicial towards Quercia and constituted reversible error.

In the dissenting opinion for Quercia v. United States, Justice McReynolds disagreed with the majority's decision to overturn Quercia's conviction due to a judge’s comments during trial. He argued that while judges should be careful in their remarks, they are not required to remain completely silent or passive throughout proceedings. In his view, it is within a judge’s purview and responsibility to question witnesses and clarify evidence as needed for justice. The comments made by the presiding judge were intended only as an explanation of why he found certain testimony unconvincing; they did not constitute an instruction on how jurors should decide guilt or innocence nor did they infringe upon their duty or authority in any way. Therefore, Justice McReynolds believed there was no reason for reversal based on these grounds.