Recently, there has been a lot of talk about Marijuana DUIs, and how states are dealing with these cases as marijuana becomes legal in those states.  The million dollar question is: What constitutes under the influence of marijuana while driving?  In other words, at what level would a person be so impaired while on marijuana that it would impact his or her driving negatively?

It is not as simple as it seems.  A recent study by AAA’s traffic safety foundation found that setting a blood test limit for marijuana is impossible.  In other words, States that drug test drivers for marijuana are not using accurate scientific methods to determine impairment.  States obviously have a strong desire to create limits for marijuana impairment in the same manner as alcohol.  Marshall Doney, AAA’s president and CEO told AP, “In the case of marijuana, this approach is flawed and not supported by scientific evidence.”

According to the study conducted by AAA, the problem with setting marijuana DUI limits is that cannabis is metabolized differently than alcohol.  The AAA study showed no correlation between high THC levels and impairment.  In other words, drivers with relatively high levels of marijuana’s psychoactive compound THC were not found to be impaired at all, while drivers with comparably low levels may be more dangerous while driving, especially if that person is not a regular user.  The study showed that there is no scientific proof that all people become impaired at an exact blood limit for THC.  Also, frequent marijuana users can be tested for high levels of THC even several days after they last used pot, while infrequent users can rid their system in considerably shorter periods of time.

Another issue with testing for THC levels in the blood is by the time police stop a driver, and by the time the blood of the driver is tested, the blood most likely has already fallen below the legal threshold because active THC dissipates rapidly.  The average time to collect blood from a suspected driver is often more than two hours because taking a blood sample typically requires a warrant and transport to a police station or hospital.

NOTE: When a driver has both been using marijuana and drinking alcohol, the two substances together greatly heighten impairment.   Studies show that mixing both will most certainly heighten impairment.


So what does all that mean for a prosecutor?  What does the prosecutor have to show to prove that a driver was impaired by marijuana in his or her driving?  Let us first look at the law.

California VC 23152(a) states: It is unlawful for any person who is under the influence of any alcoholic beverage or drug, or under the combined influence of any alcoholic beverage and drug, to drive a vehicle.

In marijuana cases, the prosecutor must prove beyond a reasonable doubt that a driver was “under the influence of marijuana” while driving a vehicle.  The fact that traces of marijuana are found in a driver’s system weeks after it has been ingested does not prove that the driver was under influence during arrest.

People v. Canty (2004) 32 Cal.4th 1266, 1278) sheds light on this proposition.  The Court in that case stated that: “To be guilty while under the influence of drugs in violation of Vehicle Code section 23152 subdivision (a), the drugs must have so far affected the nervous system, the brain, or muscles as to impair to an appreciable degree the ability to operate a vehicle in a manner like that of an ordinarily prudent and cautious person in full possession of his faculties.”

In People v. Enriquez (1996) 42 Cal.App.4th 661, 665-666) and People v Torres (2009) 173 Cal.App.4th 977, 983 also state: It is not enough that the drug could impair an individual’s driving ability or that the person is under the influence to some detectable degree.  Rather, the drug must actually impair the individual’s driving ability.


As the recent AAA study shows, the law on marijuana DUI is not settled.  As of today, there is no blood test limit on marijuana when it comes to driving.  As a result, until a uniform standard of testing marijuana impairment when driving is achieved, every marijuana DUI must be fought.  However, note that anything else mixed with marijuana is a totally different case.  In other words, other drugs and or alcohol mixed with marijuana has the effect of heightening impairment, and there are studies that show this.  Those cases do not fall within the perimeters discussed above.

If you are arrested for marijuana DUI, call the Law Offices of Jeffery Rubenstein.  (310)477-2100.  We can help.

–Philip Cho


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