OK, so say you don't disclose it because it was expunged. Then something does show up in the NCIC check, how do you explain why you lied and said you were never arrested when you definitely were arrested OR can you guarantee that an expunged case will never show up on a background check? I wondered about this before submitting my applications and I even put it out for advice on this forum at one time.
You explain it (if you have to) by saying officer I knew you weren't asking me about that situation because its been expunged and as I am sure you know its a crime in Maryland for you to ask me about that.