expungement
It sounds to me like you've been railroaded. From what I know, unfortunately in our country a person can have things on their record without it being on their record if you get what I mean. In other words a person could have several crimes not filed or without conviction remain on their record for the states allotted statutes to run their course. In Washington state where I live a misdemeanor if not filed or executed can remain for 3 years on a persons record regardless of a conviction or not. What I might suggest is that you find out if they are trying to take the back door approach, which means that they could be trying to charge you with the same thing but under a different law or statute. Expungement is a good idea, if you can do it as an adult in your state, but as far as I know they only Expunge youths and only if they have abided by the law for the period of time required until they reach the status of being an adult. In short find out if they have any intentions on correcting their mistake and if not hire an attorney.
matthew hacker