This is an audio case brief of Illinois v. Gates, 462 U.S. 213 (1983).The audio brief provides a full case analysis. However a written summary of the case is provided below.

Table of Contents


Police officers executed a search warrant in Lance and Susan Gates home. The officers discovered marijuana and other contraband in the couples’ home and automobile. The two were indicted for violation of state drug laws. 

On May 3, 1978, the Bloomingdale Police Department received by mail an anonymous handwritten letter which read as follows:

“This letter is to inform you that you have a couple in your town who strictly make their living on selling drugs. They are Sue and Lance Gates, they live on Greenway, off Bloomingdale Rd. in the condominiums. Most of their buys are done in Florida. Sue his wife drives their car to Florida, where she leaves it to be loaded up with drugs, then Lance flys down and drives it back. Sue flys back after she drops the car off in Florida. May 3 she is driving down there again and Lance will be flying down in a few days to drive it back. At the time Lance drives the car back he has the trunk loaded with over $100,000.00 in drugs. Presently they have over $100,000.00 worth of drugs in their basement.

They brag about the fact they never have to work, and make their entire living on pushers.

I guarantee if you watch them carefully you will make a big catch. They are friends with some big drugs dealers, who visit their house often.

Lance & Susan Gates


in Condominiums”

The letter was referred by the Chief of Police of the Bloomingdale Police Department to Detective Mader, who decided to pursue the tip. Mader learned, from the office of the Illinois Secretary of State, that an Illinois driver’s license had been issued to one Lance Gates, who resided at a stated address in Bloomingdale. He contacted a confidential informant, whose examination of certain financial records revealed a more recent address for the Gates, and he also learned from a police officer assigned to O’Hare Airport that “L. Gates” had made a reservation on Eastern Airlines flight 245 to West Palm Beach, Fla. He was scheduled to depart from Chicago on May 5 at 4:15 p.m.

Mader then made arrangements with an agent of the Drug Enforcement Administration for surveillance of the May 5 Eastern Airlines flight. The agent later reported to Mader that Gates had boarded the flight, and that federal agents in Florida had observed him arrive in West Palm Beach and take a taxi to the nearby Holiday Inn. They also reported that Gates went to a room registered to one Susan Gates and that, at 7:00 a.m. the next morning, Gates and an unidentified woman left the motel in a Mercury bearing Illinois license plates and drove northbound on an interstate frequently used by travelers to the Chicago area. In addition, the DEA agent informed Mader that the license plate number on the Mercury was owned by Gates. The agent also advised Mader that the driving time between West Palm Beach and Bloomingdale was approximately 22 to 24 hours.

Mader signed an affidavit setting forth these facts, together with a copy of the anonymous letter, and submitted it to a judge. The judge issued a search warrant for the Gates’ residence and for their automobile. 

At 5:15 a.m. on March 7th, only 36 hours after he had flown out of Chicago, Lance Gates, and his wife, returned to their home in Bloomingdale. They drove the car in which they had left West Palm Beach some 22 hours earlier. The Bloomingdale police who were awaiting them. The police searched the trunk of the Mercury, and uncovered approximately 350 pounds of marijuana. A search of the Gates’ home revealed marijuana, weapons, and other contraband. 

The Illinois Circuit Court ordered suppression of all these items, on the ground that the affidavit submitted to the Circuit Judge failed to support the necessary determination of probable cause to believe that the Gates’ automobile and home contained the contraband in question. This decision was affirmed in turn by the Illinois Appellate Court and by a divided vote of the Supreme Court of Illinois.

The U.S Supreme Court agreed to review the case.


Whether the informants tip as well as the officers affidavit provided probable cause for the judge to issue a warrant to search the defendant’s car and house.


In determining whether probable cause exists for the issuance of a warrant, the issuing judge or magistrate must  consider all the circumstances set forth in the affidavit before him, including the “veracity” and “basis of knowledge” of persons supplying hearsay information, that there is a fair probability that contraband or evidence of a crime will be found in a particular place.


The court begun its analysis by agreeing with the Illinois supreme court that anonymous tips alone cannot provide the basis for probable cause. The officers affidavit can lend support.

The court explained:

The Illinois Supreme Court concluded—and we are inclined to agree—that, standing alone, the anonymous letter sent to the Bloomingdale Police Department would not provide the basis for a magistrate’s determination that there was probable cause to believe contraband would be found in the Gates’ car and home. The letter provides virtually nothing from which one might conclude that its author is either honest or his information reliable. Likewise, the letter gives absolutely no indication of the basis for the writer’s predictions regarding the Gates’ criminal activities. Something more was required, before a magistrate could conclude that there was probable cause to believe that contraband would be found in the Gates’ home and car. 

The Illinois Supreme Court also properly recognized that Detective Mader’s affidavit might be capable of supplementing the anonymous letter with information sufficient to permit a determination of probable cause. 

But this is where the U.S. Supreme court broke with the Illionois Supreme court.

The court explained that In holding that the affidavit in fact did not contain sufficient additional information to sustain a determination of probable cause, the Illinois court applied a “two-pronged test,” derived from our decision in Spinelli v. United States.

The Illinois Supreme Court understood Spinelli as requiring that the anonymous letter satisfy each of two independent requirements before it could be relied on. First it had to adequately reveal the “basis of knowledge” of the letter writer—the particular means by which he came by the information given in his report. Second, it had to provide facts sufficiently establishing either the “veracity” of the informant’s informant, or, alternatively, the “reliability” of the informant’s report in this particular case.

But the U. S. Supreme Court found that the two prong test was technical and unpractical.

Instead the better test to finding if probable cause exists, according the U.S. Supreme court is to adopt the totality of circumstance test.

The court explained that  an informant’s “veracity,” “reliability” and “basis of knowledge” are all highly relevant in determining the value of his report. However, these elements should not  be understood as entirely separate and independent requirements to be rigidly exacted in every case which the opinion of the Supreme Court of Illinois would imply. Rather, as detailed below, they should be understood simply as closely intertwined issues that may usefully illuminate the commonsense, practical question of whether there is “probable cause” to believe that contraband or evidence is located in a particular place.

This totality-of-the-circumstances approach is far more consistent with our prior treatment of probable cause than is any rigid demand that specific “tests” be satisfied by every informant’s tip. Perhaps the central teaching of our decisions bearing on the probable cause standard is that it is a “practical, nontechnical conception.” In dealing with probable cause, … as the very name implies, we deal with probabilities. These are not technical.

We conclude that it is wiser to abandon the “two-pronged test” established by our decisions in Aguilar and Spinelli. In its place we reaffirm the totality-of-the-circumstances analysis that traditionally has informed probable cause determinations. The task of the issuing magistrate is simply to make a practical, common-sense decision whether, given all the circumstances set forth in the affidavit before him, including the “veracity” and “basis of knowledge” of persons supplying hearsay information, there is a fair probability that contraband or evidence of a crime will be found in a particular place. And the duty of a reviewing court is simply to ensure that the magistrate had a “substantial basis for … concluding  that probable cause existed. We are convinced that this flexible, easily applied standard will better achieve the accommodation of public and private interests that the Fourth Amendment requires than does the approach that has developed from Aguilar and Spinelli.

Our decisions applying the totality-of-the-circumstances analysis outlined above have consistently recognized the value of corroboration of details of an informant’s tip by independent police work.

In the present case, the magistrate could rely on the anonymous letter, which had been corroborated in major part by Mader’s efforts. The corroboration of the letter’s predictions that the Gates’ car would be in Florida, that Lance Gates would fly to Florida in the next day or so, and that he would drive the car north toward Bloomingdale all indicated, albeit not with certainty, that the informant’s other assertions also were true. Because an informant is right about some things, he is more probably right about other facts including the claim regarding the Gates’ illegal activity. This may well not be the type of “reliability” or “veracity” necessary to satisfy some views of the “veracity prong” of Spinelli, but we think it suffices for the practical, common-sense judgment called for in making a probable cause determination. It is enough, for purposes of assessing probable cause, that “corroboration through other sources of information reduced the chances of a reckless or prevaricating tale, thus providing a substantial basis for crediting the hearsay. 

Finally, the anonymous letter contained a range of details relating not just to easily obtained facts and conditions existing at the time of the tip, but to future actions of third parties ordinarily not easily predicted. The letter writer’s accurate information as to the travel plans of each of the Gates was of a character likely obtained only from the Gates themselves, or from someone familiar with their not entirely ordinary travel plans. If the informant had access to accurate information of this type a magistrate could properly conclude that it was not unlikely that he also had access to reliable information of the Gates’ alleged illegal activities. Of course, the Gates’ travel plans might have been learned from a talkative neighbor or travel agent; under the “two-pronged test” developed from Spinelli, the character of the details in the anonymous letter might well not permit a sufficiently clear inference regarding the letter writer’s “basis of knowledge.” But, as discussed previously, probable cause does not demand the certainty we associate with formal trials. It is enough that there was a fair probability that the writer of the anonymous letter had obtained his entire story either from the Gates or someone they trusted. And corroboration of major portions of the letter’s predictions provides just this probability. It is apparent, therefore, that the judge issuing the warrant had a “substantial basis for … concluding” that probable cause to search the Gates’ home and car existed.


 The judgment of the Supreme Court of Illinois therefore was reversed because the court found that there was probable cause for the issuance of the warrant.

Share on facebook
Share on twitter
Share on linkedin
Share on email
Share on print
Share on reddit
Share on whatsapp
Share on pinterest
Share on pocket