OK, what about states with a sticker on the license to indicate if it is expired- doesn’t this violate “probable cause” if they run a plate they can visually see is not expired, and they have no other real reason for suspicion?
The only reason I would consent to letting a cop search my car for pot is a), if I didn’t have any and b) I was on the highway and the cop said I would have to wait an hour for the drug dog to arrive from the next county.
Probable cause is required for searches and seizures. It’s pretty clearly not a seizure to run your plates, and I’m equally sure that the state doesn’t need probable cause to “search” its own computer records. Besides, running the plates will tell them whether the vehicle has been reported stolen, and probably some other good stuff (like, I think, if the owner has a restricted driver’s license, or, more definitely, if the sticker doesn’t belong to the plate).
One thing to remember is that there is legal, and there is “what’s done.”
They may not be able to act on “what’s done,” but it’s ‘done’ all the time.
I’ve been run through the system at least twice for non-suspicious, non-driving related issues. Once when my father got a job as a dispatcher for a local PD in MA, he was “playing with the system” and needed someone to run. The other was by my wife’s uncle when we started dating, run through a NH local PD’s system. (Too see if I had any shady things in my past… the last guy did…) I came up clean on both. (would have been embarrasing if Dad had found anything). Neither of these were by tag, but by name/birthdate, but the concepts are the same.
In MA, I have a friend, who was driving with a suspended license (bad to do), and was run because he had a “unique plate,” and the cop was bored… he got what he deserved in this case.
Oh, all right. SOME may call them tags. But the people I run across always call them plates.
In Ohio it isn’t public information anymore. The person requesting the info has to have a legitimate reason, such as to verify info on a job application or to get an address to serve court papers. See Ohio BMV Form 1173. Getting the address of the cute blonde you just saw in the Blue Honda with plate no. 12345 isn’t a legitimate reason.
Link:
Other side of the coin:
When I lived in Waikiki, my car was stolen and soon abandoned in front of a strip club about a mile away. The cops called to tell me to get it at the impound lot. I picked it up without incident, got it repaired, and then weeks later . . . I figured out that the plates had been expired for several months. 
In Utah I was pulled over the other day on my way to work because the trooper ran my plates and my name came up as “license suspended for medical.” This was a total surprise to me, and when he got my DL and ran that, it turned out the medical guy was someone else with my first/last name (not middle) and a different birthdate.
I live in MD. Everytime I’ve been pulled over they’re run my registration afterwards.
We don’t have them in New York, and the tags/plates don’t expire. I’ve had the same plates for maybe 10 years, and transfered them from car to car. The registration has to be renewed, and that comes in the form of a windshield sticker.
Using our in car computer system we can do both random inquiries and full inquiries on registrations and licenses. When we are doing random inquiries we enter in using a particular key (happens to be F1). Only general information will come up. Type of car, expiration etc. No personal information for the driver unless there is something wrong. If it is expired of there is a suspension then the full information comes up including name, date of birth and a picture. If there is probable cause then you hit another key (happens to be F5) and the full information comes up. That is used when you are pulling over a car, have a suspicious vehicle, are making an accident report… Although they don’t check each lookup to see if you are using it correctly there is a state audit every so often and if you are using F5 too often there better be an explaination.
Our computers check three systems for warrants. One for traffic (failure to appears, unpaid tickets) one for state criminal warrants and NCIC. The traffic system is accurate. If it pops up with a warrant it is for the registered owner. The criminal system often gives “associated hits”, maybe someone with the same birth day or name. NCIC spews out a bunch of crap(from all over the country) that very rarely has anything to do with the guy in front of you. It seems that if you have a hispanic name there will be a NCIC hit when your plate is run. Usually because one guy has been caught crossing the border about 20 times and has used a different name each time. Multiply that by how many illegals get caught and you can see how each common Spanish name can get a hit. Those false hits are very easy to toss out without pulling anyone over. Thats probably what you saw.
No. They may have to establish that they don’t discriminate in what checks they make, but they would never have to have a “reason” for running a check. Mind you, different departments may have procedures in place that prohibit doing an otherwise constitutionally valid or legal process in order to avoid someone being a discriminatory jerk. 
Oh, and by the way, in many states, license plates are referred to as “tags”, even officially, see, for example, Vermont.
EXACTLY WHICH OF YOUR RIGHTS HAVE THEY VIOLATED??
Sorry to shout, but this is the crux of the whole stupid issue. “Probable cause” is needed for only two things: searching something or someone which is private, and seizing a person or property.
Running a computer check to see what information exists in the system does neither. It does not search you or your property. It does not seize you, or your property.
Therefore, there would be no constitutional issue with an officer running a check on random tags, or even on every tag he sees.
There MAY be legal issues unrelated to the Fourth Amendment. A state can always voluntarily limit access to a database through passage of a law. And a police department, or a particular jurisdiction with some department that has police powers, could always voluntarily restrict such searches if they chose (perhaps to avoid the uneasiness of the public at having the police running checks for no other reason than to see if they have a grounds to hassle someone).
But a constitutional issue it is not. If you think it is, I refer back to the top of this answer: What Right do you think they have violated? Be specific: Scalia will insist upon it.
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Sorry, I didn’t mean just running the tags violated probable cause, I meant, what if they act on information they would not have had, and would not have acted upon, without running the tag? For example, you have visible tags that are not expired. They run the plate anyway and find the tag does not belong on your car,or that the car owner has outstanding warrants. You had valid tags, they had no reason to run the check, but now pull you over, maybe arrest you, for something they would not have been able to surmise without unnecessarily running the tag.
If my definition of “probable cause” still does not jive with this scenario , my apologies. But the definition I have includes not only search and seizure, but arrests as well.
What if the cop acts on information he never would have had if he hadn’t decided to drive down your street?
The answer to that question is: it’s perfectly legal for him to drive down your street, and if he sees a felonious assault in progress, he can make an arrest.
It’s perfectly legalf for him to run your tags through the system, and if he sees evidence of a crime as a result, he can then act.
He doesn’t need “probable cause” to run your plates. The information from running the plates may give him probable cause to act further.
Got it- I was under the impression there was some sort of distinction made between crimes an officer “happened upon” and those in which he initiated, with different procedures in each case.
Let’s distinguish, to begin with, a case where the defendant is stopped and questioned when the tag appears valid. E.g., http://www.wicourts.gov/sc/opinion/DisplayDocument.html?content=html&seqNo=27087 ; http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=il&vol=app/2003/5010958&invol=3 from a case where the sequence is reversed. In your case, the officer isn’t conducting a seizure (traffic stop) or a search (of the defendant’s person or property) when he runs the tags. Instead the officer runs the tag, finds information that creates probable cause, and then stops you. There the courts say you are out of luck:
http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=wa&vol=2001_app/45964-3&invol=3
Thanks- I did not know that police could “create” the probable cause. 
I hope this isn’t seen as a hijack, but I once had a bad experience due to cooperating with police. Someone had signed my name to a document. I agreed to be “interviewed” (read “interrogated”) and brought along copies of my actual signature and a pen to prove what I needed to prove. I was given the whole good cop, bad cop routine and charged with the crime anyway.
Not really a big deal…just had to show up in court with my proof. And by that time they had the real culprit. But now I know you should NEVER volunteer information to police officers under any circumstances where you’re being or could be accused of something.