In the United States v. Thayer case of 1907, the Supreme Court dealt with issues related to tax evasion and fraud. The defendant, Mr. Thayer, was accused of making false statements in his income tax return for two consecutive years - 1899 and 1900 - thereby evading taxes he owed to the government. He appealed his conviction on grounds that there were errors in instructions given by a lower court judge to the jury during trial proceedings; specifically regarding what constituted "willful" misrepresentation or falsification of information on a tax return form under existing law at that time. The Supreme Court upheld Mr.Thayer's conviction ruling that willfulness did not necessarily mean bad faith or evil intent but could also imply reckless indifference towards truth or falsity of statements made in one’s income tax returns. It further clarified that it was sufficient if an individual knowingly presented incorrect information without caring whether it was true or false as this would still constitute willful violation under relevant laws.

In the dissenting opinion for United States v. Thayer, Justice Harlan argued that the majority's decision to uphold a conviction based on evidence obtained through an illegal search and seizure was in violation of the Fourth Amendment rights of citizens. He maintained that such actions by law enforcement officials were unconstitutional and should not be tolerated under any circumstances. Furthermore, he contended that allowing illegally obtained evidence to be used in court would only encourage more unlawful behavior from police officers who might feel they could violate individuals' rights without facing any consequences. In his view, upholding this conviction set a dangerous precedent which threatened civil liberties and undermined public trust in law enforcement agencies.