A month after California voted to legalize marijuana, law enforcement officials throughout the state are prepping for what many view as the obvious – a jump in the number of people driving under the influence of pot.

What they’re not prepped for is less obvious – how to prove when people are driving under the influence of pot.

There is no roadside test that’s legal in California that can say, for sure, how much THC (the psychoactive ingredient of cannabis) is in a driver’s bloodstream. Research is underway that might change that, and more will be financed with pot taxes. But for now, a new test is years off. And a Sacramento legislator this month proposed a bill to legalize a THC-test that’s widely used in Europe, though that too isn’t a certainty. That legislator has tried before and failed to get that test legalized in California.

So, for now, there is no pot-driving test and there will be drivers who are impaired because they’re high on pot.

Enter cops like Fullerton Police Sgt. Scott Flynn.

He’s one of about 300 officers in Orange County trained as an official Drug Recognition Expert. He’s taken courses to learn how to recognize many signs of drug impairment for many different drugs, from marijuana to methamphetamine to pain killers.

If a Drug Recognition Expert suspects a person is driving under the influence, the person can be asked to undergo a specialized, 12-step field sobriety test designed for people under the influence of drugs.

  • Fullerton Police Officer Jae Song stops someone suspected of driving while impaired. (Bill Alkofer, Orange County Register/SCNG)

“It makes us more aware and gives us another tool to determine whether someone is impaired,” Flynn said of his training.

And in a world where pot is legal and there is no test for pot-impaired driving?

“I think it will be a very important tool.”

On a recent Friday night, Flynn patrolled with his K-9 partner Jax, a two-year-old Belgian malinois, when he spotted a man in a dark parking lot known for drug deals.

Flynn approached the man and began asking questions.

“What are you doing out here tonight? Have you taken any drugs?”

Flynn noted that the man had dilated pupils and an elevated pulse rate of 130. After noting that the man’s story changed, he arrested him on suspicion of being under the influence of a controlled substance and brought him to the station for a Drug Recognition Expert test.

Last month, the California Office of Traffic Safety awarded a $1 million grant to the District Attorney and designated Orange County as the lead training agency on drug-impaired driving for district attorney’s offices throughout Southern California.

The Traffic Safety Office since 2011 has awarded the county $4 million in grants, which have funded partnerships with the Fullerton Police Department for state-wide Drug Recognition Expert training and new testing equipment for the Orange County Crime Lab.

For now, it’s not positive that California’s passage of Prop. 64 will lead to many more cannabis-related DUIs. In Washington and Colorado, two states where recreational cannabis has been legal for a few years, data on the issue are mixed.

“In my opinion, we are with marijuana now where we were with alcohol about 30 years ago,” said Susan Price, the Orange County District Attorney’s assistant head of courts.

While Price believes there should be more and better testing for THC, and for more scientific studies on the effects of marijuana, she has no doubt that driving under the influence is dangerous.

In a disturbing trend, Price said, her office has seen a rise in the number of drivers, especially young people, with a combination of marijuana and other drugs or alcohol in their system.

“People think of marijuana as a harmless herb with medicinal value. But the bottom line is that it can impair your driving, especially when you combine it with something else,” she said. “We believe that education is key.”

Price said said the District Attorney’s Office has aggressively prosecuted drug-impaired drivers over the last several years with a unit that assigns one prosecutor to track a case from arrest through conviction.

During the 2015-2016 grant year, the prosecutors reviewed 1,086 drug-impaired driving cases and filed charged in 969 of those cases.

Price said some of the new grant money will fund training for more local prosecutors in drug-impaired driving cases, especially for marijuana. The office also plans to begin specifically tracking cases of marijuana DUIs – something that’s not now tracked as a unique category of crime.

“We expect that in light of the new legislation our workload in regards to these case will definitely increase,” she said.

But without a standard method of testing whether a driver is impaired on marijuana, cases can be hard to prosecute, Price said. Colorado’s DUI laws for marijuana set a limit of five nanograms of THC per milliliter of blood; California has not yet set a limit.

Cannabis presents a unique challenge as well – THC remains in the bloodstream long after its psychoactive effects are worn off. So, for now, a blood test can only conclude that a person took cannabis at some point in the recent past, not that he or she is impaired from it while driving.

Price said juries, for now, are presented with a range evidence, including blood levels and observations from the arresting officers. Testimony from a Drug Recognition Expert can have significant weight in court.

“We’ve taken cases as low as two nanograms and prevailed,” she said.

Defense attorneys say reliance on Drug Recognition Experts can be problematic.

“We’re putting a lot more credibility to what the officers observe, but it’s only his observation as to whether or not you did the test right,” said Orange County defense attorney Randy Collins, who has several pending marijuana DUI cases.

Collins said there are many problems with field sobriety tests – a person may have a medical condition that could affect the results, or the officer could read the instructions too fast and confuse the person.

To stay on safe side, Collins said, he advises people to wait between three to five hours to drive after smoking or ingesting pot.

The Fullerton Police Department is one of the agencies that trains other departments in drug recognition.

Fullerton Police Sgt. Jon Radus believes the county will be safer if more officers are trained to recognize the signs of driving while high.

“Drug-impaired driving is something that affects every community across socioeconomic boundaries and across city boundaries,” he said. “We’re going to continue to be proactive with our enforcement, because it will save lives.”