Orange County sheriff’s deputy Colton Walsh told the man facing him to watch the movement of his index finger as Walsh swept it across his face.

Then Walsh put the man, who had been arrested on suspicion of driving under the influence, through more tests, including shining a light in his eyes in a pitch-black room to see how his pupils dilated.

“The eyes don’t lie,” said Fullerton police Officer Eric Franke, Walsh’s supervisor in a drug-recognition-expert class and the department’s drug-recognition-expert coordinator. “The eyes give us quantifiable evidence of what’s going on in the brain.”

Walsh’s conclusion that the man was impaired by marijuana and methamphetamine was on the money: The driver later admitted to using both.

As the number of arrests for driving under the influence of drugs grows and officials anticipate even more with the legalization of recreational marijuana last November and the opening of pot shops in 2018, Southern California law enforcement agencies are scrambling to train officers as drug recognition experts, an advanced certification in which they learn how to recognize symptoms of seven categories of drugs and testify in court.

Already, Franke said, requests for the Orange County crime lab to process blood samples related to DUI-marijuana arrests has jumped 40 percent since November.

“It would be a safe assumption to say that the DUI-marijuana numbers will increase,” said Fullerton police Sgt. Jon Radus, a drug recognition instructor.

The experts use clues from 12 tests such as eye reaction, pulse rate, blood pressure, the ability to walk a tight line, muscle tone and counting to 30 with eyes closed and head tilted back to determine what, if anything, is affecting the driver.

While the drug recognition expert may not be able to nail down the exact substance in a driver’s system, he can tell jurors that the defendant was on a stimulant, depressant, inhalant, cannabis or other category of drug, and what the effect would have been on his driving. That testimony would be coupled with an officer’s observations about the motorist’s driving.

“We definitely believe this training is important, so we can incorporate expert opinions to help prosecutions,” said Torrance police Sgt. Ronald Harris, whose department has about five drug recognition experts now and is lining up other officers to be trained.

Riverside police post a minimum of four drug recognition experts at their DUI checkpoints, Sgt. Eric Detmer said.

Dan Fox, a Riverside County deputy district attorney who prosecutes DUI-drug cases, said the police experts are important because there is no legal presumed standard for impairment from drugs such as the .08 blood-alcohol content level, and some jurors still wonder why there’s so much fuss over a little bit of pot.

“It’s going to be a mitigated disaster. It’s going to be extremely difficult to prosecute marijuana under-the-influence drivers successfully,” Fox said.

That’s where the drug recognition experts come in.

They “are able to sort out all these different things they are seeing in a person and make an educated, informed opinion as to what the person has in them,” Fox said.

The police program is not without its critics. Attorneys who defend drivers accused of driving under the influence of drugs say the science behind the drugged-driving tests is questionable and the drug-recognition specialists are not the experts that law enforcement makes them out to be.

Developing expertise

Walsh, a 25-year-old jail deputy, signed up for the course in anticipation of hitting the streets.

“When I go to patrol, I want to be comfortable with this,” he said.

Another student, Chino officer Matt Bloch, 33, said he became interested in the drug-recognition program when he investigated traffic collisions caused by drivers under the influence.

“I want to get as much expertise as I can,” he said. “I want to make sure that when I do a DUI evaluation that I’m doing it the correct way every single time, that I don’t skip steps. That I don’t let anybody who is driving under the influence of alcohol or drugs slip through the cracks.”

There’s a waiting list for the classes at the Fullerton Police Department, which along with the California Highway Patrol and Los Angeles Police Department are the three agencies in California authorized to teach the Drug Recognition Expert (DRE) program.

Fullerton for years has aggressively arrested drivers under the influence of drugs, and its approach got noticed.

“We’re incredibly proud we’re in a position to make a difference,” Radus said.

“Every time they take a DUI driver off the road, they’re saving a life they’ll never see, they’ll never know, they’ll never touch,” he said.

Impaired by pot or not?

Marijuana is a depressant that causes drivers to react more slowly than they should. They fail to avoid objects in the road or sit at a stoplight for several seconds after it turns green.

Determining whether a driver is too affected by marijuana to operate a vehicle safely is difficult for a number of reasons.

There is no court-accepted roadside test to determine impairment. The San Diego Police Department uses the Drager DrugTest 5000, which, using a mouth swab, can determine the presence of marijuana. But a blood test would be required to determine the amount of a drug in a person.

And THC, marijuana’s psychoactive substance, can be stored in body fat for days or weeks after use, when the person is no longer impaired, so its mere presence does not equal impairment.

Even if a driver admits to smoking high amounts of marijuana, he might not show physical signs of impairment because people are affected differently. Drivers with low levels may be unsafe behind the wheel, experts say.

San Bernardino police Lt. Mike Madden said this “difficult conundrum for police departments to deal with” indicates a need for a test to determine impairment, much like a breathalyzer for alcohol.

Fox, the deputy district attorney, argues that drivers who have smoked marijuana are mentally impaired whether they show the physical signs or not.

“At 55 mph and a 5,000-pound car, when something goes wrong and you’re delayed even a half a second from that natural inclination to brake or that natural inclination to turn left, half a second is 50 feet. It’s a matter of life and death, and that’s the problem that is very hard to get across to people,” Fox said.

Fatal crashes involving drivers who recently used marijuana doubled in Washington after the state legalized the drug, according to the latest research by the AAA Foundation for Traffic Safety.

Deadly accidents also have increased in Colorado. Since the state legalized cannabis, marijuana-related traffic deaths have increased from 37 in 2006 to 94 in 2014.

It’s unknown how many of these crashes involved marijuana only, because other substances were often also involved.

Jury’s out on marijuana

The battle with public perception is at the heart of prosecuting cases.

Sarika Kim is a Los Angeles County deputy district attorney assigned to the DUI training and prosecution section.

She said many people – particularly jurors — believe marijuana is harmless, not accounting for the more potent strains that have been developed recently.

“It harkens back to the hippie movement, free love, smoking a joint, nobody’s hurting anybody. It’s a much different marijuana than your grandma’s marijuana. So people don’t see it as a dangerous drug,” Kim said.

Fox said the strongest strains, in which the THC is extracted, are “a long way from smoking a joint at Woodstock. It is in many respects hallucinogenic.”

Fox recalled a conversation he had with a drug-recognition expert he knows in Denver.

“You get in an elevator in a courthouse in Denver and the elevator reeks of pot, and that’s your jury pool,” Fox said.

The strength of a prosecutor’s case, Kim said, will be the officer testifying on his observations of the impairment. A successful prosecution will depend on the jury believing the officer, Fox said.

‘Not an exact science’

Matthew J. Ruff, a defense attorney in Torrance who has handled DUI-drug cases for more than two decades, has a problem with that testimony.

“What I’m finding more often than not is with the DREs, they tend to make a determination very quickly based on things they see and they hear and they tend to conform their conclusions to that,” Ruff said.

(Franke, the Fullerton drug-recognition supervisor, said students are taught to wait until the tests are complete before reaching a conclusion.)

Ruff said officers sometimes skip some of the 12 tests and that prosecutions should be based on the level of Delta-9, the psychoactive component of marijuana, in conjunction with an officer’s observations of a motorist’s driving.

“It’s not an exact science,” he said. “We’re dealing with officers who have gotten a very minimal amount of training. They’re certainly not scientists. They’re certainly not experts. They’re not anywhere near pharmacologists. Prosecutors, as hard as they try to elevate a DRE to the level of experts, it’s not that easy.”

Fox acknowledged that there are few studies on the effect of marijuana smoking on driving.

“So a lot of what the defense comes down to is there was no bad driving, or he did OK on his field sobriety test. And those are hard to overcome sometimes, but that doesn’t mean the person’s not impaired,” Fox said.

Becoming a drug-recognition expert

A police officer must complete many hours of training to be certified. The training includes:

— A 16-hour class that includes an overview of evaluation procedures, the seven drug categories, eye examinations and proficiency in conducting the field sobriety tests.

— A 56-hour class that includes an overview of the drug evaluation procedures, expanded sessions on each drug category, drug combinations, examination of vital signs, case preparation, courtroom testimony and written exam.

— A minimum of 12 drug evaluations under the supervision of a drug-recognition-expert instructor. Of those 12 evaluations, the officer must identify an individual under the influence of at least three of the seven drug categories and obtain a minimum 75 percent toxicological corroboration rate. The officer must then pass a final knowledge examination.

Source: International Association of Chiefs of Police