I'm mainly interested in criminal and marriage records......those are public records right? Aren't they found in one place on specific names?
If I recall correctly, in Florida, you can check court records. A friend of mine searched her ex-husband's. Nasty surprise!
No. You have heard of identity theft, have you not? The information needed to perform a 'background check' is the same information needed to create a false ID.
For criminal records you must address your request to the jurisdiction holding them and that jurisdiction will demand your qualifications for receiving the information.
For a marriage record you will have do address your request to the jurisdiction holding it and justify your privilege.
If it was easy everyone would do it. Tagline...
In Missouri we have case.net where you can look up any court case by many keywords. It is run by the government and very complete - I did a check on myself and found a speeding ticket from two years ago. I don't know if other states have similar systems.