There has been a bit of confusion around anonymous tips. In the case of Illinois v. Gates, the warrant was based in very large part on an anonymous letter. But the Supreme Court found a search warrant was supported by probable cause under the totality of circumstances (especially the police effort to corroborate the information in the letter). In Florida v. JL, the Court held that an anonymous tip called in regarding a person carrying a gun was not sufficient, standing alone, for reasonable suspicion. But in Navarette v. California the Court held a call in regarding an erratic driver could in fact by sufficient to conduct a traffic stop.
Legal Supplement
Florida v. J.L, 529 U.S. 266 (2000),
an anonymous caller reported to the Miami-Dade Police that a young black male standing at a particular bus stop and wearing a plaid shirt was carrying a gun.
Sometime after the police received the tip-the record does not say how longtwo officers were instructed to respond. They arrived at the bus stop about six minutes later and saw three black males "just hanging out [there]." Id., at A-42. One of the three, respondent J. L., was wearing a plaid shirt. Id., at A-41. Apart from the tip, the officers had no reason to suspect any of the three of illegal conduct
The tip in the instant case lacked the moderate indicia of reliability present in White and essential to the Court's decision in that case. The anonymous call concerning J. L. provided no predictive information and therefore left the police without means to test the informant's knowledge or credibility. That the allegation about the gun turned out to be correct does not suggest that the officers, prior to the frisks, had a reasonable basis for suspecting J. L. of engaging in unlawful conduct:
The requirement that an anonymous tip bear standard indicia of reliability in order to justify a stop in no way diminishes a police officer's prerogative, in accord with Terry, to conduct a protective search of a person who has already been legitimately stopped. We speak in to day's decision only of cases in which the officer's authority to make the initial stop is at issue. In that context, we hold that an anonymous tip lacking indicia of reliability of the kind contemplated in Adams and White does not justify a stop and frisk whenever and however it alleges the illegal possession of a firearm.
Navarette v. California, 572 U.S. 393 (2014),
After a 911 caller reported that a vehicle had run her off the road, a police officer located the vehicle she identified during the call and executed a traffic stop. We hold that the stop complied with the Fourth Amendment because, under the totality of the circumstances, the officer had reasonable suspicion that the driver was intoxicated.
The “reasonable suspicion” necessary to justify such a stop “is dependent upon both the content of information possessed by police and its degree of reliability.” The standard takes into account “the totality of the circumstances—the whole picture.” Although a mere “hunch’ ” does not create reasonable suspicion, the level of suspicion the standard requires is “considerably less than proof of wrongdoing by a preponderance of the evidence,” and “obviously less” than is necessary for probable cause …
By reporting that she had been run off the road by a specific vehicle—a silver Ford F-150 pickup, license plate 8D94925—the caller necessarily claimed eyewitness knowledge of the alleged dangerous driving. That basis of knowledge lends significant support to the tip’s reliability.
Another indicator of veracity is the caller’s use of the 911 emergency system. A 911 call has some features that allow for identifying and tracing callers, and thus provide some safeguards against making false reports with immunity.
Reasonable suspicion depends on “ ‘ “the factual and practical considerations of everyday life on which reason-able and prudent men, not legal technicians, act.”
Like White, this is a “close case.” As in that case, the indicia of the 911 caller’s reliability here are stronger than those in J. L., where we held that a bare-bones tip was unreliable. Although the indicia present here are different from those we found sufficient in White, there is more than one way to demonstrate “a particularized and objective basis for suspecting the particular person stopped of criminal activity.”
(internal citations omitted)
