In the United States v. Clark et al., 1981, the Supreme Court ruled on a case involving tax evasion and fraud. The defendants, Mr. and Mrs. Clark, had been convicted of evading federal income taxes by using an elaborate scheme to hide their assets in foreign trusts and corporations that they controlled but did not own directly. They appealed their conviction arguing that the jury instructions were incorrect because they allowed for a conviction based on willful blindness rather than actual knowledge of wrongdoing. The Supreme Court upheld their convictions stating that "willful blindness" is equivalent to actual knowledge under criminal law if it can be proven beyond reasonable doubt that a defendant was aware of high probability of facts constituting crime but deliberately avoided learning truth about those facts out of fear or unwillingness to confront them. This ruling established important precedent regarding how courts interpret "knowledge" in cases where individuals may have intentionally ignored evidence or warning signs related to illegal activities.

In the dissenting opinion for United States v. Clark et al., 1981, Justice Blackmun argued that the majority's decision to uphold a tax deficiency against Clark was incorrect because it failed to consider important aspects of the case. He contended that there were two key issues: whether or not an agreement existed between Mr. and Mrs. Clark regarding their property division in divorce proceedings, and if so, what its terms were. The Tax Court had found no such agreement existed but this finding was overturned by the Court of Appeals which held that there indeed was an implied agreement based on state law (California). However, Justice Blackmun disagreed with both courts' interpretations as he believed they did not adequately analyze California law nor apply it correctly to determine if any implicit understanding could be inferred from Mr. and Mrs.Clark’s actions during their divorce process.