If the off-duty Spokane firefighter involved in a triple-fatal crash earlier this year had taken even two of the four medications he had prescriptions for at the time of the collision, he could have been too impaired to drive, a drug interaction expert said Friday.

Firefighter David Batty told investigators at the Jan. 20 crash scene on Highway 2 that he had been authorized by a doctor to take Hydrocodone and Gabapentine, two painkillers; Soma, a muscle relaxant; and Ambien CR, a sleep aid, according to a court document. Batty later told an investigator, “My doctor never told me not to drive when he prescribed the medication.”

Batty told a Washington State Patrol trooper at the scene of the crash that “he had recent back surgery and was currently on medication for pain,” according to Superior Court documents.

Raymond Quock, a Washington State University professor of pharmacology and neuroscience, said, “If he (Batty) gets the prescriptions from a pharmacy, any of those medications would have warning labels about driving impairment.”

Batty was prescribed to take 350mg Soma, 10mg Hydrocodone, 600mg Gabapentine and Ambien CR. Quock said all four drugs are nervous system depressants.

Dr. Gary Franklin, medical director for the Washington Department of Labor and Industries, said it’s possible for a person on stable doses of a pain medicine, such as Hydrocodone, to drive just fine.

But Quock said combining the drugs could cause serious impairment. If a person takes more than one of those drugs at a time, the impact of drowsiness is exponential, he said.

“It’s not an additive effect. It’s a super additive effect,” Quock said.

On Jan. 20, Batty was driving south on Highway 2 behind a Plymouth Voyager minivan when he saw the van’s brake lights come on. Batty told investigators the van began to spin, and he slammed on his brakes, but realized he was going to hit the van.

Batty clipped the van, and it went into the lane of oncoming traffic, officials said. Batty’s truck spun out into a ditch. A Toyota in the northbound lane hit the minivan; the three men in the van – Michael D. Edwards, Kalen E. Hearn and Gregory S. Stueck – died at the scene.

Two days after the crash, Batty called one of the investigators, who asked the firefighter if there was anything he could have done to avoid the crash, according to the court document. Batty stated he didn’t think he was following too close to the van, and then said: “I saw him tap his brake lights, and I thought he was testing the road, so there was a short time where I didn’t react because most people tap their brakes to check the road at this time of year.”

No one else involved in the crash is under investigation, officials said.

A drug recognition expert who contacted Batty at the crash scene tested whether the off-duty firefighter’s eyes showed any signs of impairment and determined they did not, according to the court document. The expert was not able to use other tests, such as having Batty stand on one leg or do a walk and turn, because of his surgery.

Batty volunteered a blood sample, but the results have not been revealed.

He has been on medical leave from the Fire Department for several months due to an on-the-job injury, officials said.

State Patrol Sgt. Ken Wade is one of the key investigators of the Jan. 20 crash.

“We are in the process of talking to everybody who might have some knowledge about this situation,” he said.