You are able to clean your criminal record on any of your characters ONLY when you change your name and it's going to cost you 100,000$ in total (name change + clean new criminal record). There's no option to clean only your criminal record, because it's impossible to do IRL, thus non-RP.
So basically, if you want a clean criminal record, I'd advise you to start Roleplaying a new character.
/changemyname is the command, a simple name change costs 50k and if you want that criminal record cleaned, you'll have to pay additional 50k as mentioned above - 100k in total.
Yes I know, it shouldn't ask for the additional 50k for cleaning the record since you're starting a new character, but it was made that way to prevent players from abusing it (changing their name constantly to keep a clean criminal record).