ok now are you really a cop in nor cal? mine is a Misdemeanor... so it may be possible to become a cop and long as i show no doing wrong in anything ...
Yes I am, and I am also a background investigator and sergeant.
Keep in mind that your expungement will mean nothing to law enforcement as law enforcement is permitted to access that information even though it might be expunged.
Some agencies are more tolerant than others, but there i no state or federal prohibition against employment as a peace officer with ANY misdemeanor conviction. In most agencies, they would likely want to see about 5 years between the time of application and the DUI, but that number varies by individual circumstance. In the intervening time - no matter how long or short - the agency will want to see what you have done to show that you are now responsible and mature and NOT making the same mistakes that led to the prior conviction. And, yes, they will likely seek a copy of the police report so they have all the details.
We had one guy who applied here who had a DUI conviction and swore he had learned his lesson. We late found out that in the previous four or five years he had a steady string of contacts for alcohol related disturbances outside of some nightclubs and bars in neighboring jurisdictions - no arrests, but a half dozen contacts in three years. Needless to say he was not hired.