FAIRFIELD, CA (WCMH) – A California man is facing a DUI charge, but the only drug found in his system was caffeine.

KCRA reports 36-year-old Joseph Schwab was driving home from work in August, 2015 when an alcohol beverage control agent pulled him over.

The agent said Schwab was driving erratically and she believed he was under the influence of drugs. A field sobriety test revealed dilated pupils.

Schwab agreed to a blood test, but the only drug that showed up was caffeine.

Experts say that although caffeine is a drug, it’s not typically associated with impaired driving, and might even help with driving.

Schwab’s attorneys told KCRA they are stunned at the charge, but prosecutors say they plan to move forward with the case.

The prosecutor said they believe Schwab was under the influence of a drug they don’t screen for.

“This is a case without a blood result, right, so it makes it a very difficult challenge to prove in court to not have the blood result,” said Solano County District Attorney Krishna Abrams.

Schwab says that more than a year later, this whole ordeal has hurt him financially and damaged his reputation.

“Looks like I’m undependable,” Schwab said. “And when you tell this type of story to somebody, they are naturally not going to believe you.”

Schwab’s attorney is asking for charged to be dismissed, saying that driving under the influence of caffeine is not a crime.