Companies can and certainly do request your NCIC information, both for wants (warrants) and criminal history. It's also checked for any 5 or 10 year background check for an airport ID, and usually a company ID, and most employers obtain it as part of pre-employment screening. It's generally done through your state Bureau of Criminal Investigation (BCI). It takes about fifteen seconds.
I'm not certain I understand the question. The poster is not very forthcoming with information, but from what's been posted, we learn that he had a DUI, and at some point quit flying. Weather this involved commecial flying or not is unclear, as is the issue of weather or not he quit voluntarily.
What is not unclear is that if you apply for a medical certificate, you are required to report previous infractions. That one isn't debatable. What is also clear here is 14 CFR 61.59(a)(1), which states that no person may make or cause to be made any fraudulent or intentionally false statement on any application for a certificate or authorization.
You stated that you have checked the National Driver Register and determined that no record of your DUI exists, but that it does exist with NCIC, in your III (criminal history) file. The FAA does not routinely check criminal history files, but other investigative agencies do, and certainly employers do. An example of this surfaced recently in California with a number of individuals claiming disability and still holding medical certificates...not a criminal history issue, but an example of crosschecking two unrelated databases to catch a violator.
In your case, you may be up against something far more simple. I believe you stated that your prior infraction was twelve years ago, which puts it within the time frame for mandatory reporting of motor vehicle violations under the current regulation. Presently, any discrepancies between an old medical certificate application in the computer database and a new one, are flagged for investigation. If you made false statements on a prior claim and change to a different statement today, this may raise a flag.
Again, I'm not sure I understand your question, but it appears that you may be asking for advice on how to beat the system, or how to "not get caught." That's not advice anybody can, or should give you.
The best counsel you've already been given; consult with a competent attorney who specializes in FAA matters. As others have stated, AOPA carries a database listing a number of attorneys who may be able to help.
With respect to your basic question, weather to report or not report, the regulation dicates that you must disclose past violations convictions. You seem to be hinting at the idea that you might get away with not reporting if nobody is going to check your criminal history...don't go there. You'll eventually get caught, and even making the attempt is a criminal act for which stiff penalties apply. It's not something you want hanging over your head. Contact that attorney before you do anything else. You may find with the right counsel that your problem is smaller than you think.
