In Virginia, Expungements are only available for cases that have been dismissed. Either a "not guilty" verdict or certain other types of dismissal would be required. There is no expungement available for cases that were dismissed after completion of a "251 Program" or certain other types of "first offender dismissals" where community service, guilty pleas, court costs or certain other requirements were imposed.
The standards for expungements make it easiest for folks who have absolutely no other criminal record. For folks who have some prior record, then the standards make it more difficult to get a dismissed case expunged.
My advice would be to retain counsel to handle this for you. These cases can be a bit tricky, and once denied by the Court, that would be hard to fix. I have seen plenty of folks come into court on their own for this, and many of them do get their expungements. This would have to be done in Circuit Court however, and I can't think of any instances where I would advise a client to go into Circuit Court without an attorney.
If you are filing for an expungement in Fairfax County by yourself, the clerks office will give only limited help. You will have to obtain fingerprints and arrange for service on the Commonwealth's Attorney. After they are served, you have to wait 21 days for your court date and then you will be called before a Judge, usually on a Friday morning.
Arlington County has its own rules and forms for the expungement procedure.
The Virginia code reads to say that a person would be entitled to an expungement if it is a dismissed misdemeanor and no other criminal record. However, it also leaves room for the Commonwealth to object for cause, and their likely objection would be a lack of "actual innocence". At that point, they also argue that there is no detriment to the existence of the records, unless you have also alleged and offered some proof of discrimination with respect to employment, credit, or otherwise.
The preamble to the expungement chapter says:
§ 19.2-392.1. Statement of policy
The General Assembly finds that arrest records can be a hindrance to an innocent citizen's ability to obtain employment, an education and to obtain credit. It further finds that the police and court records of those of its citizens who have been absolutely pardoned for crimes for which they have been unjustly convicted can also be a hindrance. This chapter is intended to protect such persons from the unwarranted damage which may occur as a result of being arrested and convicted.
This language negates the proposition that every dismissal necessarily mandates an expungement.