## Facts

- Bloomingdale, Illinois police received an anonymous letter alleging that Lance and Susan Gates were trafficking drugs and describing a planned trip: the wife would drive to Florida to pick up drugs, the husband would fly down later and drive the car back with drugs in the trunk, and drugs were stored in their basement.
- A police officer verified parts of the letter, including the Gateses’ address and that Lance Gates had a reservation for a flight to Florida.
- Law enforcement surveillance confirmed Gates took the flight, stayed overnight in a motel room registered to his wife, and left the next morning with a woman in a car bearing Illinois plates registered to him, driving north toward Illinois.
- An Illinois judge issued a search warrant for the Gateses’ residence and car based on an affidavit attaching the letter and describing the corroboration.
- Executing the warrant, police found marijuana and other contraband in the car trunk and in the home.
- Illinois courts suppressed the evidence, concluding the affidavit failed the Aguilar–Spinelli informant-tip framework.
- The U.S. Supreme Court granted review and reversed.

## Issues

1. Whether probable cause for a search warrant based on an informant’s tip is governed by the rigid Aguilar–Spinelli two-pronged test or by a totality-of-the-circumstances approach.
2. Whether, under the proper standard, the corroborated anonymous letter supplied probable cause to search the Gateses’ home and automobile.

## Decision

- The Court reversed the suppression order and held the warrant was supported by probable cause.
- The Court rejected Aguilar–Spinelli as an exclusive, mandatory test and adopted a totality-of-the-circumstances approach for informant-based probable cause.
- The corroborated predictive details in the anonymous letter provided a substantial basis for the issuing judge to find a fair probability that contraband would be found in the specified places.
- The Court declined to decide whether to modify the exclusionary rule because the issue had not been presented to or decided by the state courts.

## Legal Principles

- Probable cause for a warrant requires a practical, common-sense determination, considering all circumstances in the affidavit, whether there is a fair probability that contraband or evidence of a crime will be found in a particular place.
- Informant “veracity,” “reliability,” and “basis of knowledge” are relevant considerations, but they are not independent prerequisites; deficiencies in one may be compensated by strengths in others or by other indicia of reliability.
- Corroboration of an anonymous tip—especially detailed, predictive information about future actions—can support an inference that the informant had reliable access to information about criminal activity.
- Reviewing courts should give great deference to the issuing magistrate and ask only whether the magistrate had a substantial basis for concluding probable cause existed, rather than conducting a de novo probable-cause determination.

## Conclusion

The Court held that probable cause based on informant tips is assessed under a totality-of-the-circumstances standard, and that an anonymous letter substantially corroborated by police investigation can provide a sufficient basis for a warrant to search a residence and vehicle.


Illinois v. Gates, 462 U.S. 213 (1983)