Driving under the influence of alcohol or drugs under California Vehicle Code 23152(a) VC and California Vehicle Code Section 23152(b) VC is one of the most widely charged criminal offenses in the LA area. Each day and night, law enforcement officers from the Los Angeles Police Department, California Highway Patrol, Los Angeles County Sheriff's Department and other agencies patrol the streets and freeways of Los Angeles looking for impaired drivers. Under the law it is a crime to operate a motor vehicle while under the influence of drugs or alcohol or with a blood alcohol content of 0.08 percent or above.

Unless the suspected drunk driver is stopped as part of a DUI checkpoint operation, a law enforcement officer must have probable cause that a driver is violating the law before the officer can legally justify stopping the vehicle. This is usually a violation of a vehicle code provision, such as speeding, improperly changing lanes or an equipment violation. Once a driver has been stopped, the officer must then be able to objectively form the opinion the driver is intoxicated. This is typically based on symptoms of intoxication, such as an odor of alcohol, bloodshot or watery eyes or slurred speech. At that point, the officer will usually ask the driver to submit to a series of field sobriety tests designed to determine if the driver is impaired. The officer may also request the driver to breath into a Preliminary Alcohol Screening ("PAS") device to see if the driver has a high blood alcohol content.

Once the officer concludes the driver is impaired, he or she will arrest the driver for DUI and will take the driver to the police station or hospital for further, more accurate chemical testing. The driver will be given the option of providing a breath or blood sample at the station (or hospital for blood). If the driver refuses testing, he or she can still be charged with a DUI offense and can lose their license for a full year.

During the Los Angeles DUI arrest process, the arresting officer will provide a notice of impending license suspension from the DMV. At that point, the driver will spend the night in jail. They may be released and provided a future court date or may have to appear in court for their arraignment the following day.