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Illinois v. Gates

Brief Fact Summary. The police received an anonymous letter outlining specific details about the Defendants, Gates and others (the “defendants”), plans to traffic drugs from Florida to Illinois. When the details were corroborated by the defendants’ actions, police obtained a search warrant and found drugs, weapons and other contraband in the defendants’ home and automobile.


Facts. The police received a highly detailed anonymous tip that the defendants were trafficking drugs. The police, following up on the tip, observed the defendants conducting specific activities which were outlined in the tip. On the basis of the tip and the defendants’ corroborating activities, the police obtained a search warrant. Upon execution of the warrant, the police found drugs, weapons and other contraband in the defendants’ automobile and home.

Issue. May a magistrate issue a valid warrant on the basis of an anonymous tip where there is no indicia of the informer’s “basis of knowledge” if the information contained in the tip is corroborated with police findings?
Since some of the anonymous tips were not corroborated and actually proved false, the informant’s “credibility/reliability” was undermined and therefore the warrant should not have been issued. Police cannot use findings of an illegal search to substantiate a previously issued warrant.

Concurrence. Even if the factual findings by police were only corroborated by innocuous behavior, a valid warrant could still have been issued because the defendants’ actions were suspicious. The main focus should be whether there is an inference, based upon the suspects’ actions, that the informant is credible and the information was obtained in a reliable manner.

Discussion. “Credibility/reliability” and “basis of knowledge” of an informant are very relevant in determining the value of a tip. These elements alone do not form the entire basis of inquiry in deciding whether probable cause exists. So long as the magistrate had a substantial basis for concluding a search would uncover evidence of wrongdoing, the Fourth Amendment is not violated.