If you are charged with DWI, one of the first things any good DWI attorney is going to ask you will be, "Why did the officer stop your vehicle?" The reason for this is simple, the 4th Amendment to the United States Constitution affords you privacy and protection from unwarranted search and seizure. The only requirement a government agent must meet in stopping your car is "Reasonable Suspicion". What's not so simple is the answer to the question, "What is reasonable suspicion?"
Reasonable suspicion is supposedly a lower standard than what most people are familiar with, namely probable cause. Reasonable suspicion is generally viewed as particularly articulated facts, as viewed by a reasonable officer in accordance with his/her training and experience, that would give reasonable inference that criminal activity is afoot. The simple way to put this is that police need more than a hunch to pull you over. Often times a bad tag, speeding, excessive swerving, or other traffic violations are all that an officer needs to get you over and begin the investigation. At this point cues of impairment can be observed and the probable cause for DWI investigation/arrest is ripened.
The reason your DWI attorney should analyze this pre-stop reasonable suspicion, is because the United States Supreme Court has created a doctrine referred to as the Exclusionary Rule. This doctrine is intended to protect you from unwarranted harassment and seizure by police. If no reasonable suspicion exists to stop your vehicle, or if the reasonable suspicion articulated by the officer is in that area of gray, a successful suppression motion at trial will bar all evidence obtained after the "illegal" stop under the Exclusionary Rule. Successful suppression of the stop means the state has no evidence to proceed on after the traffic stop, and any DWI charge will be necessarily dismissed. This serves as an important balance against vast police authority, and it's potential to be abused. However, recent changes in the high courts threaten to weaken our 4th Amendment protections by reducing reasonable suspicion quite a bit.
Settled case law in NC doesn't allow anonymous tips for law enforcement to justify stopping your vehicle. Now that doesn't mean police can't follow you and watch for other violations or indications of impairment in your driving that would corroborate the tip and justify a stop, but an anonymous tip alone hasn't been enough in the past for a stop. Anonymous tips are uncorroborated, and the officer is essentially operating off of an unreliable, unidentified statement to justify impeding your freedom of movement. Now many question how long this will last, because on April 22nd the U.S. Supreme Court decided Navarette v. California, effectively opening up anonymous tips dispatched from 911, as reasonable suspicion to stop a vehicle under suspicion of impaired driving. This will then open the vehicle and it's passengers to whatever investigation the officer can justify at that point, whether it is DWI related or not.
In Navarette v. California, the U.S. Supreme Court held that an anonymous tip to 911, where the tipster claimed a vehicle had run off the road, was reliable reasonable suspicion for an officer to believe the driver was impaired. This means the officer never saw it happen, it was just an anonymous phone call dispatched out to the officer. No further corroboration was needed, no significant swerving, no breaking a traffic law otherwise, etc. Currently in NC, the state high court rulings don't support Navaratte's more relaxed version of reasonable suspicion. Whether or not NC will adopt this lowered standard for the state is yet to be seen, but probably will be revealed before too awfully long as I believe it will be hotly litigated.
I still believe that anonymous tips in NC are not enough for the stop. Our system of Constitutional Law requires states, under Supremacy Clause rules, to follow federal law that would preempt conflicting state law. However, when it comes to affording Constitutional rights, states need only provide the bare minimum protections afforded by federal law. States are always free to enhance and heighten those standards to offer even more protection than the federal law. That would seem to be the argument in NC currently, provided you are stopped on suspicion of DWI based on an anonymous tip alone and Navarette comes up to bite you. These cases have rolled across my desk already since Navarette came out a few weeks ago, and the district attorneys are already smiling about it. Your DWI attorney needs to be prepared to suppress stops based on anonymous tips under the more stringent NC Constitutional standard. And as concerned champions of freedom, we can only hope our state will adhere to a balanced, reasonable standard that will keep us safe on the highways and protect our seemingly fading freedom of privacy.