Photo by Torrey Bailey
A research coordinator demonstrating the driving simulator at UCSD\'s Center for Medicinal Cannabis Research
In passing Proposition 64 with 56.24 percent support on election day, California legalized recreational marijuana, finally making progress on a process that began 20 years ago. While Californians age 21-and-up can now smoke in the privacy of their homes, grow six plants and possess up to an ounce, driving under the influence of marijuana remains against the law.
“It has always been illegal to drive under the influence of a drug or alcohol,” said Scott Wahl, public information officer for the San Diego Police Department, in an email. “Prop 64 hasn’t changed that. The theory (of some) is there will be an increase in DUI offenses that are marijuana related as it is now legal to consume. We will therefore have more DUI marijuana drivers on the road. Time will tell if that is the case.”
An increase of DUIs relies on whether driving under the influence of marijuana corresponds to impaired driving, a discussion that has become a point of nationwide debate.
Nine states have zero tolerance for marijuana detection in drivers, while six states have per se laws, which set a THC limit. According to the National Highway Traffic Safety Administration, such per se laws are not sufficiently backed by research.
“Determining whether a person is impaired due to cannabis is not as clear cut as it is with alcohol, particularly when it comes to driving,” said Thomas Marcotte, co-director of UC San Diego’s Center for Medicinal Cannabis Research. “With alcohol, there’s a fairly straightforward relationship with your blood-alcohol content, your breath-alcohol content and level of impairment,” said Marcotte. “When you blow into the breathalyzer, higher numbers are usually accorded to worse performance on the road. THC is different, it’s more complicated. When you first smoke, the numbers go very high in your blood, and then they drop fairly rapidly even though you’re still high and may be impaired.”
California legislation falls in a grey area, where law enforcement officers must prove impairment through driving ability, field sobriety tests and chemical tests in order to warrant a DUI. Before Proposition 64, the smell of marijuana alone was enough justification for a police officer to search a car. Under new state law, that’s not the case, but the scent can be a giveaway to another violation.
“Obviously if it [smells like] burnt marijuana, it would show it was recently consumed,” said San Diego County NORML Executive Director Michael Cindrich. “Fresh marijuana would just show that it was in the vehicle… Although this is a new law, I foresee police officers using the smell of marijuana for probable cause to believe that there is an open container in the passenger compartment of the vehicle, which is in violation of the law.”
Like alcohol, open containers of marijuana must be out of the driver’s reach.
If a police officer assumes a driver is under the influence based on swerving, straddling lanes or traveling considerably below the speed limit, the driver is subject to a field sobriety test. This procedure has remained unchanged since the passing of Proposition 64. Drivers are asked, but not required, to walk the line, say the ABC’s, and balance on one foot like a suspected intoxicated driver would.
“Field sobriety tests are not very reliable for marijuana because there aren’t a lot of specific tests related to marijuana, and there’s a lot of subjectivity regarding an officer’s observations,” Cindrich said. “Someone may not be able to balance on one foot, but that may be because they have a bad leg, are tired, are nervous, or aren’t wearing a good pair of shoes or the pavement isn’t flat. There are a lot of reasons.”
To supplement the field sobriety test’s shortcomings, an officer takes observations into account, such as whether the driver’s eyes are bloodshot and watery or whether their speech is slurred.
But the state is searching for a surefire way to determine whether a high driver is perilous and has commissioned UCSD’s Center for Medicinal Cannabis Research to find the solution. Starting in January, the center will use a driving simulator to test volunteers’ impairment levels before and periodically after they smoke marijuana of various THC content. Blood, urine and saliva samples will also be collected to track whether these chemical tests show a correlation between THC quantity and performance levels.
“There’s a lot of studies out there that look at cannabis and cognition,” Marcotte said. “There’s a lot of studies that look at cannabis and driving, but there’s not many studies that try to put them all together.”
The UCSD study zones in on cognitive ability, such as deciding whether it’s safe to continue through a yellow light, turn left in front of oncoming traffic or multitask. For example, the driving simulator can initiate an incoming call on the monitor, prompting the volunteer to divert their attention to an accompanying screen where they have to locate a symbol, all while controlling the wheel. The goal is to imitate the actions a driver would go through if their phone rang, or they needed to check their GPS.
Aside from putting cognitive skills to the test, UCSD is using this study to create an iPad application for officers to use during a traffic stop when drivers are suspected of being high.
“It’s gotta be something that can be easily explained if it’s 3 a.m. on a freeway with cars going by,” Marcotte said. “Coordination is one thing that gets impaired with cannabis, such as hand-eye coordination and being able to track things. So there will be an object that moves on the screen that you need to be able to track. There will be certain divided attention tasks where you need to do two things at once. We’ll be looking at memory tasks, since memory gets really impaired by cannabis.”
Volunteers will be tested on the app after every completed driving simulation, so that the app could hit the ground running soon after the three-year study wraps up in Spring 2019.
“Not everyone’s an easy, laid-back stoner,” Marcotte said. “There could be some people that are aggressive, and we’re trying to work with the California Highway Patrol to make sure that we actually have something that is implementable, and if it proves to be successful, it’s something that they would consider using.”