California Vehicle Code Section 23152(e) says it's unlawful to drive while under the influence of a drug
You may be guilty of this crime if you are under the influence of drugs which were prescribed to you by a doctor, an illegal drug or even over-the-counter drugs if it can be proven they affected your ability to drive such that it made your driving while under the influence of a drug. The punishment for driving under the influence of drugs mirror those for driving while intoxicated.
Overview of Proof in California DUI Drug Cases
Proving a person violated this law is not necessarily easy. The key for the Prosecution in proving drug cases is often whether the drug actually causes a significant or sufficient level of mental or physical impairment at the time of driving. The prosecutor must show that the drug actually impaired your driving. It is often impossible for the prosecutor to prove driving impairment based upon drugs. This is especially true where the charge is based ONLY on drug use and not the combination of alcohol with a drug. Interestingly, there are a number of drugs which may enhance your ability to drive; in some cases, the forensic or scientific evidence will be in the driver's favor. The DUI Prosecutor will try to prove the drive was under the influence of drug(s) by introducing evidence related to driving patterns, (often ambiguous) physical signs and symptoms, field sobriety testing performance and chemical tests.
Overview of Defense in California DUI Drug Cases
It can be a defense if the drug causes one to drive with the same caution characteristic of a sober person or ordinary prudence under the same or similar circumstance.It is a defense if the driving pattern, (often ambiguous) physical signs and symptoms, field sobriety testing performance and chemical tests are just as consistent with non-impairment as they are with impairment.If charged with driving under the influence of prescription medication, sleep driving may possibly be a DUI defense in California. But the involuntary intoxication should be based on an unanticipated reaction to medication taken as lawfully prescribed.
Jury Instruction for VC 23152(e) - DUI
California Criminal Jury Instruction Number 2110. Driving Under the Influence (Veh. Code, 23152(e)/(f)) A person is under the influence if, as a result of taking a drug, his or her mental or physical abilities are so impaired that he or she is no longer able to drive a vehicle with the caution of a sober person, using ordinary care, under similar circumstances. The manner in which a person drives is not enough by itself to establish whether the person is or is not under the influence of a drug [or under the combined influence of alcohol and/or a drug]. However, it is a factor to be considered, in light of all the surrounding circumstances, in deciding whether the person was under the influence.