I'm giving this a four rating for a couple of reasons. Although individuals who are druggies, alcoholics, or criminals are undateable in my book, it actually depends on the nature of the person's background.
For example, if some guy I was dating was caught stealing a Snickers bar from 7-11 when he was 13 and he regretted doing it, then it's fine by me (we all do stupid stuff when we're young).
Or maybe he did experiment with drugs/alcohol and decided not to do them anymore, then that's fine, too. If he used to be a druggie/alcoholic and is now sober, then he's also dateable just as long as he doesn't go back to his old habits.