Most DMVs will give out personal information. I believe more states are stopping this and that Florida and Texas do not give out this info anymore.
Most criminal information is public information and is very easy to obtain.
You can get it yourself by going through local court documents or hire an agency to do it for you for a fee. You do not need to be a PI or law enforcement official to obtain criminal records. As a PI you might have more resources available simply because you will learn about how to obtain this information more easily, but you don't have any more right to it than an ordinary citizen. I am searching for a man that got a 15 year old girl pregnant 3 years ago and left the state. Now she needs support and he is no where to be found.