In California, Penal code section 484 is Petty Theft, and is only a MISDEMEANOR. however, if someone has a prior theft related conviction, and is arrested for Petty Theft, the prior elevates it to a felony, Penal code section 666/484, commonly referred to as Petty Theft with a Prior. That charge is a wobbler, meaning it is both a felony or a misdemeanor. If your son was placed on probation and completed it without any violations, even if it was a felony, it can then be reduced to a misdemeanor and expunged, although the Navy would still be aware of it. If he was denied probation and sent to prison, it is a felony and cannot be reduced.