Illinois v. Gates: Supreme Court Case, Arguments, Impact

How totality of the circumstances relates to probable cause

A judge bangs a gavel

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Illinois v. Gates (1983) dealt with the admissibility of evidence, particularly anonymous tips to the police. The Supreme Court applied the "totality of the circumstances test" instead of a rigid two-pronged test developed under previous decisions.

Fast Facts: Illinois v. Gates

  • Case Argued: October 13, 1982, March 1, 1983
  • Decision Issued: June 8, 1983 
  • Petitioner: State of Illinois
  • Respondent: Lance Gates et ux.
  • Key Questions: Did the use by the Bloomingdale, Illinois, police department of anonymous letters and a police affidavit as probable cause to conduct a warrant-less search of the home and car of Lance Gates and his wife violate their Fourth and Fourteenth Amendment rights?
  • Majority Decision: Justices Burger, White, Blackmun, Powell, Rehnquist, and O'Connor
  • Dissenting: Justices Brennan, Marshall, and Stevens
  • Ruling: Although previous cases had established the requirements of a "two-pronged" approach, the majority found for Illinois, stating that the totality—combined letter and police work producing an affidavit—could be used as probable cause. 

Facts of the Case

On May 3, 1978 detectives at the Police Department of Bloomingdale, Illinois, received an anonymous letter. The letter alleged that Lance and Susan Gates were engaged in an illegal drug smuggling operation. According to the letter:

  1. Ms. Lance would leave her home in Illinois on May 3 and drive to Florida.
  2. Once in Florida, her car would be loaded with drugs.
  3. Ms. Lance would fly back to Illinois.
  4. Mr. Lance would fly from Illinois to Florida a few days later and drive the car and drugs back home.

The letter also alleged that Lance's basement had over $100,000 in drugs.

Police began to investigate the matter immediately. A detective confirmed the car registration and address of the couple. The detective also confirmed that Lance Gates had booked a flight from O'Hare airport in Illinois to West Palm Beach, Florida on May 5. Further surveillance from the Drug Enforcement Agency on and after May 5 revealed that Lance Gates got on the flight, got off the flight in Florida, and took a taxi to a hotel room registered in his wife's name. The couple left the hotel in a car registered to them and drove north-bound on a route towards Chicago.

The detective from the Bloomingdale Police Department submitted an affidavit, notifying a judge of his observations, and attached the anonymous letter to it. A circuit court judge reviewed those documents and issued a search warrant for the Gates' home and car.

The police were waiting at the Gates' home when they returned from Florida. Officers found 350 pounds of marijuana in the car, as well as weapons and other contraband in their home.

The circuit court ruled that the affidavit and anonymous letter were insufficient to establish probable cause for police to search the car and home. The Illinois Appellate Court affirmed that decision. The Illinois Supreme Court bench was divided on the issue and the U.S. Supreme Court granted certiorari to settle the question.

Constitutional Question

Did the police violate the Gates' Fourth and Fourteenth Amendment rights when searching their home and car? Should the court have issued a search warrant based on the anonymous letter and police observations?


The arguments focused on whether or not the "credibility" and "basis of knowledge" for the anonymous letter could be established. Attorneys for the Gates' argued that the anonymous letter could not be used to show probable cause because it was anonymous. The author could never be shown to be reliable, one of the key standards for a two-part test for probable cause.

Attorneys arguing against the suppression of the letter maintained the opposite. The detective's affidavit in addition to the anonymous letter provided sufficient grounds for a search of the Gates' home and car. The search warrant had not been improperly issued and the evidence should not be suppressed.

Majority Decision

In a 7 to 3 decision delivered by Justice William Rehnquist, the Supreme Court ruled that the anonymous letter and affidavit could be used to establish probable cause to issue a search warrant. The Gates' constitutional rights had not been violated.

The Court argued that its rulings in two previous cases, Aguilar v. Texas and Spinelli v. United States, has been misapplied.

Lower courts had "rigidly" applied a two-pronged test from those rulings in order to assess probable cause. The test required the court to know:

  1. the "veracity" or "reliability" of the informant.
  2. the informant's "basis of knowledge"

The anonymous tip that police had received about the Gates' home failed to provide that information.

According to the majority opinion, a "totality of the circumstances" approach would better help determine when there is probable cause to issue a warrant on the basis of an anonymous tip.

Justice Rehnquist wrote:

"[P]robable cause is a fluid concept—turning on the assessment of probabilities in particular factual contexts—not readily, or even usefully, reduced to a neat set of legal rules."

"Veracity," reliability," and "basis of knowledge" should be considerations for the court, rather than rigid guidelines. The totality of the circumstances approach, according to the majority opinion, allowed magistrates to use common sense when making probable cause determinations, rather than asking them to follow rigid guidelines that might not fit the case in front of them.

In applying the totality of the circumstances test, the court found that the anonymous tip and affidavit established probable cause for a search warrant. There was a "fair probability" that the writer of the anonymous letter received the information from the Lance or Susan Gates or someone they trusted, according to the majority opinion.

Dissenting Opinion

In two separate dissenting opinions, Justices William J. Brennan, John Marshall, and John Paul Stevens argued that the totality of the circumstances approach should not be used in place of the two-prong tests in Aguilar and Spinelli. "Veracity" and "basis of knowledge" should remain the two required factors for issuing a finding of probable cause. If some of the informant's claims could be proved false, the anonymous tip would fail to provide a basis of knowledge for the court. In the Gates' case, detectives had no way of proving when Susan left Illinois. She also failed to take a plane from Florida to Illinois as the anonymous tip had suggested. As a result, the judge should not have determined there was probable cause to search the Gates' home and car.


The court extended the "totality of the circumstances" approach to anonymous tips corroborated by police statements. Instead of solely focusing on "veracity" and "basis of knowledge" to make probable cause determinations, magistrates issuing warrants could take other common sense factors into account. This loosened restraints on courts in terms of issuing search warrants.


  • Illinois v. Gates, 462 U.S. 213 (1983).
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Your Citation
Spitzer, Elianna. "Illinois v. Gates: Supreme Court Case, Arguments, Impact." ThoughtCo, Aug. 28, 2020, Spitzer, Elianna. (2020, August 28). Illinois v. Gates: Supreme Court Case, Arguments, Impact. Retrieved from Spitzer, Elianna. "Illinois v. Gates: Supreme Court Case, Arguments, Impact." ThoughtCo. (accessed June 10, 2023).