A great question for a labor / employment attorney because there are industries in which this will need to be reported. Good luck.
The response above is not intended as legal advice since it’s impracticable to provide thorough, accurate advice based upon the query without additional details. It is highly recommended that one should seek advice from a criminal defense attorney licensed in your jurisdiction by setting up a confidential meeting. Moreover, this response does not constitute the creation of an attorney-client relationship since this message is not a confidential communication because it was posted on a public website, thereby publicly disclosing the information, which is another reason to setup a confidential meeting with an attorney.
My response to you is based on the following assumption: That you were previously convicted of a felony charge, but you were later able to expunge the violation. If that is the case, then you are entitled to the benefit of the 1203.4 expungement in that your conviction has been set aside, a not-guilty plea was entered and the matter was dismissed. However, expungements have limitations. You are still required to disclose your conviction in response to any government entity, to the CA State Lottery and if you want to pursue a politics. The other issue is whether or not you attempted to reduce your offense to a misdemeanor before you expunged it. Your question is not very detailed, therefore, I cannot provide you with a detailed response. It does appear that you definitely need to consult with a criminal attorney to determine what happened in your case as it relates to the expungement. Before you choose to derail your employment path, get a free consultation. Many attorneys on AVVO provide free consultations.
Your question really is not related to criminal defense. It is probably something a career counselor can handle much better. An employment attorney, as Mr. Cernyar suggested, would be a good person to as about the effect of having a felony showing up on a background check. In terms of how to respond to an employment application asking about convictions, generally speaking you can mark no because of the expungement, but it would matter on the specific application on how it is worded and who is the employer.