UCSD Researchers Remain Focused on Developing Marijuana Sobriety Test

Currently, there is no reliable roadside check to see whether drivers are actually impaired from smoking marijuana, which was legalized for recreational use in California at the start of this year.

“We have a reliable and easy-to-use test to measure blood alcohol concentration. But right now we don’t have a fast, reliable test to gauge whether someone is too doped up to drive,” writes Dr. Igor Grant, Chair of the Department of Psychiatry at UC San Diego and Director of the Center for Medical Cannabis Research (CMCR).

Under the Medical Marijuana Regulation and Safety Act, the California Legislature asked UC San Diego to research the effects of smoking marijuana on driving ability in 2016. Led by Dr. Thomas Marcotte, Associate Professor of Psychiatry and Center Manager of the CMCR, the research project focuses on determining how long drivers can be impaired after smoking, finding an alternate method of testing for THC besides blood tests, and experimenting with cognitive tablet tests that can potentially be used to decide impairment, in addition to establishing a relationship between the dosage of marijuana and driving.

Marcotte’s team is having groups of volunteers inhale different doses of THC, including one group with zero percent of THC as the placebo group. Afterwards, the volunteers go through a series of tests, including tablet tests and driving simulations. The results will not be not known until the end of the study, since researchers are remaining blind as to which volunteers are placebo and which volunteers inhaled active cannabis, according to Marcotte.

Prior to the legalization of recreational marijuana, the number of DUI drug arrests has almost doubled in the San Diego area over a year, with the San Diego Police Department making 112 arrests in 2016 and 207 arrests in 2017, according to San Diego Police Department Traffic Analysis.

The issues with testing for weed-impaired drivers are that tolerance can be built by smoking marijuana more frequently and a high THC concentration does not necessarily correlate to impacted cognitive functions, according to Grant. Unlike alcohol, setting a THC concentration limit does not work in checking to see whether a driver is affected by marijuana.

“There is kind of a disconnect between the blood levels and how impaired you really are,” Grant said to Southern California Public Radio (SCPR). “You could have a high level if you tested somebody immediately and they wouldn’t be very impaired, or you could have a low level, and you could be impaired.”

In March 2017, SDPD received two Drӓger-5000 machines from the San Diego Police Foundation to help determine whether drivers are impaired. If a driver is pulled over after exhibiting symptoms of driving under the influence, they are first subjected to the Standardized Field Sobriety Test to determine whether any impairment is present, which consists of walking in a straight line, standing on one foot, and following the horizontal path of a moving finger with their eyes. .

The driver can be subjected to the Drӓger test if they fail the previous test. The Drӓger test is a mouth-swab test that works for seven different drugs, including marijuana. A swab is run inside the mouth and inserted into a machine to check for the Delta-9-THC compound, the chemical that causes the high.

If the test is positive and the officer decides that the driver has been driving under the influence of drugs, the driver is brought to the police station where a drug recognition expert (DRE), like SDPD Officer John Perdue, examines their condition by observing their behavior and administering psychological tests.

Officers can become a DRE by completing a drug evaluation training, which consists of a 72-hour classroom training course and a field certification course. As of Jan. 23, SDPD has 13 DREs and 10 officers in training, with more classes coming in the future, according to Perdue.

Although the Drӓger test can help officers decide whether a driver is drug-impaired or not, several projects throughout the state testing the accuracy of the Drӓger test have concluded that it has inconsistent results, with several false positives and negatives.

“The Dräger-5000 is a helpful tool but ultimately the onus will still be on the officer to show impairment,” Perdue said.

In addition, the high cost of the Drӓger test makes it difficult for police departments to ensure all squad cars are equipped with the machine. SDPD’s two Drӓger-5000 machines cost $6,000 each, and they were only stationed at certain DUI checkpoints at the time.

Despite the increasing pressure for police enforcement and the government to stop stoned driving, especially with the legalization of recreational marijuana, Marcotte warned against any premature legal actions on cannabis-related driving laws, such as establishing a concentration limit, because the science may not necessarily support it.

Currently, Marcotte and his team are a third of the way through the project, with about two years left.

Cynthia Leung is a staff writer at The Triton.