Top 10 Cases for Police Series, Part 2

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Editor's Note: With so many cases affecting policing, the question often arises regarding which are the most important. If a law enforcement professional could choose only 10 cases to examine, which would those be? Included in this series is a list of what experts Rolando del Carmen and Jeffery Walker consider to be the top 10 cases most influencing day-to-day policing in the U.S. Continuing from our last installment, in reverse order, we give you number 9: Illinois v. Gates, 462 U.S. 213 (1983).


The two-pronged test for probable cause established in previous cases is superseded in favor of the “totality of circumstances” test.


On May 3, 1978, the Bloomingdale, Illinois, police department received an anonymous letter containing the following statements: that Gates and his wife were engaged in selling drugs, that the wife would drive her car to Florida on May 3 to be loaded with drugs, that Gates would fly to Florida and drive the car back to Illinois, that the trunk would be loaded with drugs, and that Gates had more than $100,000 worth of drugs in his basement. Acting on the tip, a police officer obtained Gates’ address and learned that he had made reservations for a May 5 flight to Florida. Arrangements for surveillance of the flight were made with an agent of the Drug Enforcement Administration. The surveillance disclosed that Gates took the flight, stayed overnight in a hotel room registered in his wife’s name, and left the following morning with a woman in a car bearing an Illinois license plate, heading north. A search warrant for Gates’ house and automobile was obtained on the basis of the officer’s affidavit setting forth the foregoing facts and a copy of the anonymous letter. When Gates arrived at his home, the police were waiting. A search of the house and car revealed marijuana and other contraband. Gates was charged with violating state drug laws and was convicted.


Did the affidavit and the anonymous letter provide sufficient facts to establish probable cause for the issuance of a warrant? YES.

Supreme Court Decision

The two-pronged test established under Aguilar and Spinelli is superseded in favor of a “totality of circumstances” approach. The task of an issuing magistrate is to make a practical decision whether, given all the circumstances, there is a fair probability that the evidence of a crime will be found in a particular place.


“Unlike a totality of circumstances analysis, which permits a balanced assessment of the relative weights of all the various indicia of reliability (and unreliability) attending an informant’s tip, the ‘two-pronged test’ has encouraged an excessively technical dissection of informants’ tips, with undue attention being focused on isolated issues that cannot sensibly be divorced from the other facts presented to the magistrate.”

Case Significance

The two-pronged test for establishing probable cause in cases in which information is given by an informant is modified and superseded by the “totality of circumstances” test, making it easier for police officers to establish probable cause for the issuance of a warrant. Under the two-pronged test as enunciated in Aguilar v. Texas, 378 U.S. 108 (1964), probable cause based on information obtained from an informant could be established only if the following were present: (1) reliability of the informant and (2) reliability of the informant’s information. Both conditions must have been satisfied before probable cause could be established. In contrast, under the “totality of circumstances” test, probable cause may be established if, based on all the circumstances (including hearsay), there is a fair probability that contraband or evidence of crime will be found in a particular place. The Gates case still preserves the two-pronged test established in Aguilar, but it does not treat the two aspects separately and independently. Instead, the “totality of circumstances” approach is used, meaning that whatever deficiencies there may be in one prong can be supplemented or overcome by the other, together with other available evidence.

For many more cases, see Briefs of Leading Cases in Law Enforcement, 8th ed., which includes short, easy-to-understand briefs of 185 cases of primary importance to law enforcement officials.


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