If a case was filed and subsequently dismissed by the DA you are not going to be eligible for a finding of factual innocence. An expungement will do nothing for you at this point.
Mr. Driessen is a former Deputy DA in Orange County with over 8 years of criminal law experience. Nothing stated on this site shall in anyway be construed as legal advice, or as creating any attorney client relationship. If you would like to hire Mr. Driessen, feel free to contact him at www.theocduiguy.com.
Court records will not be destroyed. A check of court records under your name and date of birth will show what happened, including the dismissal by the DA and that you never admitted guilt.
Your arrest will always show on law enforcement records, but should not show on the 'background checks' which these shysters offer to anyone who pays. However, your case itself will show up on the background check, as well as the dismissal.
Note that if the DA dismissed the charges after a not-guilty plea by you, you have not been "convicted" of anything.