LOS ANGELES (CBSLA.com) — An elite unit of the Los Angeles Police Department can tell if someone is under the influence of prescription or illegal drugs without ever having to wait for lab results.

The officers, known as “Drug Recognition Experts” (DRE), undergo an intensive training program so they’re able to pinpoint the signs and symptoms of seven different drug categories while they’re patrolling the streets.

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“You have dissociative anesthetics, which is your PCP. Narcotics and analgesics…that’s your heroin, Vicodin, it’s your Oxycontin,” said the LAPD’s Doug McCombs.

At first, the DREs are taught to conduct a standard sobriety test in a classroom of volunteers.

The officers then gradually learn to identify drugs using the same 12-step evaluation procedure.

“If you’re under the influence of heroin, you’re gonna be nodding off,” said Officer David Marroquin. “You might have someone who’s fidgety.”

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Marroquin added, “Alcohol does this to somebody… and drugs do something else. And if we didn’t have the knowledge that DRE gives us, we would just be a normal patrol officer.”

The LAPD has more than 130 DREs who work in about every division citywide.

KCAL9’s Sharon Tay reported that prosecutors and city officials rely on the drug experts in a court of law.

“Your observations are evidence, so it’s important that you’re precise…in not only how you document it, but also how you interpret it,” said Sgt. Mike Delgadillo.

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Tay said the DRE program is being practiced in other states after its success in Los Angeles.