Yes. California Vehicle Code Section 23152(E) makes it illegal to drive a vehicle under the influence of drugs.
Charges can be filed for driving under the influence of marijuana. While there is no breathalyzer for marijuana, an officer can arrest you on suspicion of DUI based on objective symptoms of drug use, and a poor performance on field sobriety tests. Once arrested, a blood test is administered and the sample is later analyzed by a crime lab to determine if charges should be filed by the District Attorney.
Interestingly enough, Oakland-based Hounds Labs Inc. is developing a marijuana breathalyzer. For an article on this new technology, click the link below:
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