"if they were expunged, it never happened"
In theory, yes. In reality... not always. I saw an instance where a trader filing a U4 had to reply to the NASD that the arrest was expunged. He figured it wouldn't appear as a "disclosure" in CRD, but it did. And, the NASD had no problem with it, but because he was actually fingerprinted, it appeared.
They don't "expunge" fingerprint reports, regardless of what the cops may tell you- they're always in the database.
Or, so I've been told.