Law review: DUI of pot is new territory

Jim Porter
Jim Porter

We all know about blood alcohol tests to determine if someone is driving under the influence of alcohol. Urine and blood tests are accurate regarding how much alcohol is in someone’s system and the law is relatively clear as to when drinking too much violates the law.

The law is less clear when it comes to the use of marijuana. As our court case recently opined: “Currently there is no test similar to a BAC test for alcohol that accurately determines a person’s level of impairment from lipophilic drugs such as marijuana.” 

Smoking pot all morning

Nineteen-year-old Davion Murphy and his buddies smoked marijuana, ate breakfast, went to a car wash and basically hung out before Murphy drove off in his silver Lexus. Surveillance footage from the car wash clearly showed all four friends smoking something and witnesses later testified it was marijuana, not cigarettes.

Later Murphy ran a red light in Lancaster, near his home, as he was traveling approximately 88 mph in a 40 mph zone. 

Murphy’s Lexus broadsided the driver’s side of a Subaru killing all three passengers. Neither Murphy nor his passengers were seriously injured in the accident. But of course. 

Murphy was charged and convicted of second-degree murder — implied malice. 

Testing level of impairment from smoking pot

At Murphy’s trial a toxicologist testified that there is not yet a test similar to a blood alcohol test for determining impairment from consuming marijuana. The toxicologist stated that they use carboxy and hydroxy concentrations to calculate “some rough estimates” about when someone last used marijuana. A measurement of carboxy THC can show marijuana in a person’s body weeks after the person last used the drug.

The toxicologist testified that the highest concentration of marijuana reaches the brain and brings potent psychoactive effects about 90 minutes after smoking. Marijuana use tends to have more mental than physical effects.

She testified that “marijuana use imposes challenges to a driver’s ability to safely operate a motor vehicle, including impairing focus on the road and affecting reaction time.” Murphy’s blood test showed plenty of marijuana.

The jury convicted Murphy of second-degree murder and sentenced him to three concurrent terms of 15 years-to-life in prison. He appealed.

Second degree vehicle murder

Murphy appealed claiming there was inadequate proof that he was the driver and that he acted with malice, as opposed to mere negligence.

Under the California Penal Code, murder is “the unlawful killing of a human being with express or implied malice a forethought … malice is ‘express’ when a person manifested a deliberate intention to unlawfully take the life of another human being; it is ‘implied’ when there was no considerable provocation or when the circumstances attending the killing showed an abandoned and malignant heart.”

“Malice may be implied when the defendant does an act with a high probability that it would result in death and does it with a base antisocial motive and with a wanton disregard for human life … a conscious disregard for the danger to life.”

The Court of Appeal for the Second Appellate District upheld the jury’s conviction determining there was substantial evidence to support a finding of implied malice for Murphy’s second-degree murder conviction.

Based on the quantity of psychoactive THC in Murphy’s blood, the toxicology expert hypothesized that a similarly situated person would likely have been actively impaired at the time of the collision. Furthermore, all of the circumstances point to Murphy’s conscious disregard of the dangers he posed to the lives of others on the roadway. Conviction upheld.

            Jim Porter is an attorney with Porter Simon licensed in California, with offices in Truckee and Tahoe City, California, and Reno, Nevada. These are Jim’s personal opinions. Jim’s practice areas include:  real estate, development, construction, business, HOA’s, contracts, personal injury, accidents, mediation and other transactional matters. He may be reached at or

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