I don't know what my colleague is talking about. There is no expungement procedure in CA which will seal arrest records. An expungment will result in the dismissal of a conviction but the original arrest and conviction will still appear on your record along with the notation "conviction dismissed."
There is a procedure you can go through on the simple arrests to establish your factual innocence. If you succeed your records will be sealed and destroyed. This would not help with your DUIs.
A so-called "expungement" will not seal the records of your DUI convictions. What's more, the DUIs will show up on your DMV record for ten years, so your employer will learn about them if your job involves driving, or if you are listed on the employer's car insurance policies.
m not as enthusiastic about so-called "expungements" as some other lawyers. There's a link to a very informative article about Mel Gibson's "expungement" of his DUI conviction, which talks about the limited value of this procedure.
Under Penal Code §1203.4, a person who is granted probation can apply to have the case dismissed after probation is complete. This is sometimes called an expungement, but it doesn't really expunge anything or seal your record. The conviction is still a part of the court's public records, which will also show the case was dismissed. You still must disclose the conviction when applying to be a police officer or for certain other jobs, or if asked on an application for a state license or to run for public office. The conviction can still be considered a prior offense, so your DUI conviction could be used to increase the punishment in subsequent DUI convictions.
BEWARE of law firms that promise to "clear your record" and charge thousands of dollars. The process of filing a Penal Code §1203.4 petition is pretty simple, and you can do it yourself with forms available from the court clerk's office, especially if you completed probation without any problems. If you had a probation violation along the way, you may want an attorney's help, but the guys who charge thousands to file simple paperwork will probably overcharge you for that, too.
California Labor Code §432.7 says employers can't ask about any arrest that didn't result in a conviction, inquire about it from other sources or use it in a hiring decision.
Some attorneys interpret this Labor Code section to mean you don't have to disclose a conviction that was dismissed under Penal Code §1203.4, but I usually advise clients to disclose it, with an explanation that the conviction was subsequently dismissed.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like this site, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.