California Vehicle Code Section 23152 (a) makes it illegal to operate a motor vehicle while under the influence. If you notice, there is no requirement of being over a certain blood alcohol level to be found guilty of this section. That means that even if your BAC comes back under .08%, the District Attorney still can, and oftentimes does, charge you with a DUI if the police officer reports that you failed the Field Sobriety Tests. This section is also applied to drugs and can result in you being charged with DUI while under the influence of marijuana, prescription drugs, or illegal substances.
California Vehicle Code Section 23152(b) makes it illegal to drive with a .08% or more Blood Alcohol Content (BAC). There is no requirement of proving you were impaired to be charged and convicted of VC 23152(b), the fact that you have a BAC of .08 or higher within three hours of driving is enough evidence in and of itself. Any person who is pulled over for an alcohol-related DUI in California is usually charged with both VC 23152(a) and VC 23152(b), but only one punishment may be imposed. The punishment for violating either section is the same.