http://en.wikipedia.org/wiki/Illinois_v._Gates
In May 1978, the Bloomingdale, Illinois Police Department received an anonymous letter. [alleging criminal activity]
<snip>
Mader signed an affidavit laying down the events as they had unfolded, in addition to the anonymous letter. A judge of the Circuit Court of DuPage County issued a warrant. Upon the Gates' arrival home, the Bloomingdale Police searched the car, recovering over 350 lb. of marijuana. A search of the Gates' residence led to the discovery of additional marijuana and weapons.
The Illinois Circuit Court decided that the search was unlawful based on the test established in the Supreme Court ruling in Spinelli v. United States. In essence, the affidavit did not provide enough evidence to establish probable cause, which led to the exclusion of evidence obtained on the basis of that warrant. This ruling was upheld by both the Illinois Appellate Courts and the Supreme Court of Illinois.
The case was brought to the United States Supreme Court when the state and several amicus curiae, friends of the court, asked them to review the decision. The main question that was presented was, May a judge issue a search warrant on basis of partially corroborated anonymous informants tip?
The Supreme Court overturned the ruling of the Illinois courts. Justice William Rehnquist delivered the decision. In a 6-3 ruling, Illinois won the case. Justice Rehnquist stated:
We agree with the Illinois Supreme Court that an informant's "veracity," "reliability" and "basis of knowledge" are all highly relevant in determining the value of his report. We do not agree, however, that these elements should be understood as entirely separate and independent requirements to be rigidly exacted in every case[...] [T]hey should be understood simply as closely intertwined issues that may usefully illuminate the common sense, practical question whether there is "probable cause" to believe that contraband or evidence is located in a particular place.
This rejected the Aguilar-Spinelli test and put in place a totality-of-the-circumstances standard. This was put into place because the court recognized that there was more evidence that the Gateses were involved in drug trafficking than just the letter standing alone.
The court agreed that if the letter had just stood alone it would not be probable cause to get a warrant. The court also recognized that under the Aguilar-Spinelli two-pronged test, it would be very hard for the reliability prong to ever be satisfied from an anonymous tip so it therefore should be abandoned.
This case is a landmark case in the evolution of probable cause and search warrants. In this case, the Supreme Court abandons the Aguilar-Spinelli Test.
http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=case&court=us&vol=462&page=213
IOW, an
anonymous tip with at least
some form of corroborating 'evidence' (and that could be defined very loosely, IMO) = probable cause for a search warrant.
Scary, eh?
