In the case of Illinois v. Gates et ux., 1982, the U.S. Supreme Court established a new standard for determining probable cause in search and seizure cases under the Fourth Amendment. The court ruled that an anonymous tip could provide sufficient basis for establishing probable cause if it was corroborated by independent police work. Previously, courts had used a two-pronged test to determine whether an informant's tip could establish probable cause: assessing both the credibility of the informant and their basis of knowledge. However, in this case, Justice Rehnquist argued that these elements should not be rigidly applied but rather considered as part of a totality-of-the-circumstances approach where they are relevant considerations among many others when evaluating overall reliability.

In the dissenting opinion for Illinois v. Gates, Justice Brennan argued that the majority's decision to abandon Aguilar-Spinelli test in favor of a "totality-of-the-circumstances" approach weakened Fourth Amendment protections against unreasonable searches and seizures. He contended that this new standard was too vague and subjective, allowing law enforcement excessive discretion in determining probable cause based on anonymous tips. Furthermore, he expressed concern about potential abuses of power by police officers who could use unverified information as grounds for obtaining search warrants or conducting investigations without sufficient evidence. He also criticized the majority's reliance on post hoc rationalizations to justify their decision rather than adhering to established legal principles and precedents.