First of all, congrats on your achievements (not the minor conviction of course). "Expungement" is a term of art used by us attorneys in California - technically, your conviction can never be erased, but an "expungement" will allow for dismissal of the charge and a notation on your rap/dmv record that reflects that. That said, your "conviction" was very minor in the grande scheme of things, so I don't think it would affect your law school admissions or becoming an attorney at all.
Based on your facts it sounds like the citation might have been dismissed-after you completed the alcohol awareness school and wrote the paper. I really do not believe that this minor incident will have any bearing on your law school applications. You should be proud of your achievements and the fact that you learned a good lesson from this event. Good luck. My colleague was correct with his response about expungments.
I disagree with both of the prior answers to the extent that they refer to "expungements." There is no such post-conviction remedy in California law, and yours is exactly the kind of matter that points up the lack of utility in the use of that term.
You haven't identified the statute of which you were convicted, and the court procedure that you describe sounds more like a Deferred Entry of Judgment than it sounds like a Penal Code Section 1203.4 dismissal. If your conviction was to an infraction, there is no need to disclose to the Bar. If you did a satisfactory DEJ, it may be that there is no need to disclose to the Bar. In all events, it is critical to make a precise and accurate determination as to the state of your criminal record before you file your application with the Bar.
I recommend that you utilize the CA Attorney General Live Scan service. That is the same data base as is utilized by the State Bar. (Google "Live Scan" for info about where and how to get this record, and the small fee for the service.) Whatever is revealed there is what you need to deal with.
The important question here is what you need to disclose. The Bar is far more concerned about your integrity in making the required disclosures than it is about a single incident of a couple of beers in a parking lot. It is fair to consider the application itself an integrity test.
If you run into difficulty with admission after making a full and fair disclosure on your Bar application (and I am NOT predicting that you will), there are some attorneys in your area with remarkable records of success in this field. You can email me then if you need any of those names. For now, get the specific information you need. You will find in law practice, that there is no substitute for accuracy and precision in fact-gathering.
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