The U.S. Supreme Court ruled Tuesday that police can stop and search a driver based solely on an anonymous 911 tip.

The 5-4 decision split the court's two most conservative justices, with Justice Clarence Thomas writing for the majority and Justice Antonin Scalia penning the dissent.

In August 2008, an anonymous 911 caller in California phoned in a report that a pickup truck had run her off the road. The caller gave the location of the incident, plus the make and model of the truck and the license plate number.

Police subsequently pulled over a truck matching that description and smelled marijuana as they were walking toward the vehicle. Officers eventually found 30 pounds of marijuana in the truck and arrested the driver, Jose Prado Navarette.

Navarette challenged the search and arrest as unconstitutional, arguing that officers did not have reasonable suspicion to pull him over in the first place because police knew nothing about the identity or reliability of the tipster.

The five-justice court majority disagreed, and in so doing gave police new authority to rely on anonymous tipsters.

The court has long held that officers can make stops based on anonymous tips, but the information in those tips must provide enough detail to give rise to a reasonable suspicion of criminal activity. In this case, Thomas, the author of the majority opinion, concluded that because the 911 tipster said she had been forced off the road, she was an eyewitness, and that police could infer that there was reason to believe the truck driver was drunk.

Relying on 911 tipsters is reasonable, he said, because "a 911 call has some features that allow for identifying and tracking callers," and the calls can be recorded.

In a scathing dissent, fellow conservative Scalia called the Thomas opinion a "freedom-destroying cocktail" that would encourage "malevolent" tipsters to make false reports. It matters not whether the caller gave details about her alleged accident. The issue, said Scalia, is "whether what she claimed to know was true."

As to the inference that the truck's driver was drunk, Scalia pointed out that the police officers here followed the pickup for over five minutes — and "five minutes is a long time" — without any indication of drunken driving or even bad driving.

"After today's opinion," said Scalia, "all of us on the road, and not just drug dealers, are at risk ... "

Joining Scalia in dissent were three of the court's more liberal members: Justices Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan. Joining Thomas in the majority were Chief Justice John Roberts and Justices Anthony Kennedy, Samuel Alito and Stephen Breyer, who defected from the court's liberal bloc to provide the fifth and decisive vote.

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