Criminal convictions cannot generally be expunged. Generally a criminal conviction will remain on your record for the rest of your life. If you are convicted and sentenced under the "First Offender" act, and you successfully complete your first offender probation, you are entitled to a "discharge", but generally the arrest will remain on your record.
You should always consult with (and hire) a local attorney experienced in criminal defense when you or a loved one are accused of a crime. After conviction it is nearly impossible to get a case reversed, but before conviction there are many things an experienced criminal defense attorney can do to assist in preventing a conviction.