There are many reasons you would want to expunge your arrest record. Expungements are available ONLY to those people who have not been convicted of the charged crime. If you have been convicted, you cannot seal your record. Most people want to seal their record because the arrest, or arrests, are getting in the way of a good job. Some are embarrassed about an arrest that can be easily found on the internet. Others simply want to get rid of a charge that never should have happened in the first place.
Expunging an arrest record begins when you make your first appearance in court for the charge. You cannot plead guilty or you will not be eligible for an expungement. If you plead no contest, or nolo contendre, you will not be eligible.
Two special circumstances exist with misdemeanor crimes of domestic violence and with marijuana possession. Even though you may ultimately have the charges dismissed, most courts require you to plead guilty or no contest. This makes you ineligible for an expungement.