On April 22, the Supreme Court ruled on Navarette vs. California, http://www.supremecourt.gov/opinions/13pdf/12-9490_3fb4.pdf a case which called into question the validity of a traffic stop based only on an anonymous 911 tip. The justices ruled 5-4 in favor of the stop, saying in the majority opinion: "The traffic stop complied with the Fourth Amendment because, under the totality of the circumstances, the officer had reasonable suspicion that the truck’s driver was intoxicated."
The case comes from an August 2008 call to the Mendocino County 911 center reporting a pickup truck, suspected drunk driver, forcing a vehicle off the road. The caller gave a specific description of the car including the plate. The caller did not give his or her name, but given the fact that it was a 911 call, the dispatchers certainly had the caller's phone number. The pickup was located and an officer smelled marijuana coming from the truck. A search of the truck netted about 30 pounds of marijuana and the arrest of Lorenzo and Jose Navarette. They were later convicted of marijuana trafficking. They appealed, claiming an unreasonable stop in violation of their 4th Amendment rights.
Officers get anonymous tips, BOLOs, and "attempt to locate" calls all day long. A great deal of them are anonymous, but the officer is duty-bound to try to locate the alleged wrong-doer and, if found, investigate. What do you do when you find the vehicle or person who is alleged to have committed a crime? If the officer doesn't see any wrongdoing, then the officer has to make a reasonable decision based on what he or she knows. Every circumstance is different, and the justices in this case seemed to make an effort to limit the scope of Navarette vs. California, but the message was clear, and in my opinion, the right one. If it went the other way, then officers would have their hands tied if they locate the subject of a BOLO and can't investigate any further.
So what is the best practice when dealing with anonymous tips? My experience is that you have to evaluate the totality of the information you have. Like any other call for service, you have to go on what you know and what you see. It's always best, when dealing with a vehicle on the highway, to spot a violation yourself and articulate it in the official record. A probable cause stop based on a traffic violation is the best scenario, but that isn't always what happens. This is where the experience of the officer in evaluating and reporting what he or she knew at the time of the stop is invaluable to a successful prosecution.
In Navarette, the report was that a truck was being operated recklessly, therefore creating a hazard to other motorists. The officers had to try to find the car and investigate. What if they let it go without interdicting and the driver went on to kill somebody? I think the important factors that the officers are assumed to have considered in Navarette are: the tipster reported it right after it happened so most likely there wasn't time to make up a set of facts, the report was of a nature to create a public hazard, the caller was very specific in the vehicle description and license plate. There was no doubt that they had the right truck when they made the stop.
So what is the take away from Navarette vs. California? I think it should be that officers can and should act on a reasonable tip that a crime is being committed. Like every other call you handle involving a report of a crime, you have to evaluate every bit of information, use every bit of your experience and training, and make a reasonable and defensible decision on how to act. If dealing with a vehcile on the street, try to add your own observations to the mix to make the reason for the stop that much more defensible. In the end, you'll have to write your criminal report with as much detail as possible about what facts and circumstances you considered before you took action.