When someone gets arrested for driving under the influence (DUI) in California, they not only have a criminal case to deal with — they also have to fight the Department of Motor Vehicles (DMV). The moment they are taken into custody, the law enforcement officer will swap their driver's license with a 30-day temporary one.
Defendants then have to contact the DMV within ten days of the arrest to request a DMV Hearing at the Drivers Safety Office – which is like a small-scale trial – to argue against the license suspension. When defendants hire a criminal defense attorney right away, the lawyer can request this hearing and appear on their behalf to present evidence and cross-examine witnesses like the arresting officer.
Note that first-time offenders who do lose the DMV hearing can usually continue driving as follow a few steps to get their driving privileges reinstated.