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San Diego Police Are Using Swab Tests for Marijuana DUIs

2 minute Read

With weed now legal in California for adults 21 and over, lawmakers have been working on how to regulate marijuana DUI’s.

In San Diego, they’ve turned to swab tests. With a donation of two Dräger DrugTest 5000 machines from the San Diego Police Foundation, cops debuted them on the streets this past St. Patrick’s Day.

The machine tests for marijuana, in addition to cocaine, opiates, methamphetamine, amphetamine, methadone, and benzodiazepines. However, it’s only able to test for the presence of these substances, but not the level of intoxication.

“It’s a huge concern of ours with the legalization of marijuana that we’re going to see an increase in impaired drugged driving,” said Police Chief Shelley Zimmerman. “We want to get these impaired drivers off the streets.”

States such as Colorado have seen an uptick in driving under the influence. Within a one year period between July 2015 and July 2016, DUI citations in Colorado rose from 316 to 398. However, the guidelines for marijuana DUI’s are hazy.

“You can’t look at blood and nanograms of THC {the main psychoactive compound in cannabis} and conclude if someone is impaired,” says Mary Celeste, a former Denver County Court judge and expert witness in marijuana DUI cases. “There’s more things to look at, like individual metabolism rates and THC potency.”

In 2014, Colorado lawmakers concluded that any driver who tested above five nanograms of THC per milliliter of blood would be not be deemed guilty per se, but would have the benefit of “permissible inference” to determine if they were actually impaired. Not everyone who has five nanograms of THC in their system is necessarily too impaired to drive.

The most serious limitation with technology like swab testing is that it’s simply a detection test, says Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws (NORML). “{It} should not be conflated with impairment testing,” he tells Jane Street. “Ultimately, if law enforcement’s priority is to better identify drivers who may be under the influence of cannabis, then the appropriate response is to identify and incorporate specific performance measures that accurate distinguish those cannabis-influenced drivers from those who are not, such as via the use of modernized Field Sobriety Tests, training additional Drug Recognition Evaluators, or even the use of computer-assisted performance technology such as” That would be better than relying on screening bodily fluids for detection, he adds which “are not consistently associated with behavioral impairment.”

Dräger’s DrugTest 500 premiered in the United States in 2009 and has been used by law enforcement all over the country and the world. In San Diego, they’ll be used primarily at DUI checkpoints. To use it, a driver must run a mouth swab inside their mouth for up to four minutes before the swab is placed in the machine with a solution. After six to eight minutes, the machine will say which substances, if any, are present.

The machine only looks for THC, as opposed to other cannabinoids, or chemical compounds in cannabis, which don’t get you high. It only detects active THC, however, instead of also inactive THC, which can remain in your system for weeks.

Not every driver will be forced to take the test — only those who the police suspect might already be impaired. They’ll be looking for clues such as bloodshot eyes, blank stares, and the odor of cannabis, according to San Diego police Officer Emilio Ramirez.

If a driver refuses to take the swab test, the police can force them to take a blood test. When you smoke cannabis, THC levels in the bloodstream can rise rapidly to about 100 nanograms per milliliter, before declining to less than 10 nanograms within the hour. Blood tests best detect recent use and measure active THC in the blood stream. For chronic users, THC can remain detectable in the blood for a few days.

While evidence from the swab test will be admissible in court, it shouldn’t have an effect on how DUIs are prosecuted. Moreover, California law still does not have a threshold for how much THC a person can have in their system before they’re considered too impaired to drive — but again, this number would nonetheless vary from person to person.

San Diego Police Are Using Swab Tests for Marijuana DUIs